This short term is well-known to everyone who has at least some experience with development. But not everyone understands what exactly it means and why it is needed. Developer Peter Gazarov talked about the API in simple words on his blog.
The abbreviation API stands for “Application Programming Interface” (application programming interface, application programming interface). Most large companies at some stage develop APIs for clients or for internal use. To understand how and how APIs are used in development and business, you first need to understand how the World Wide Web works.
World Wide Web and remote servers
The WWW can be thought of as a huge network of interconnected servers on which every page is stored. An ordinary laptop can be turned into a server capable of serving an entire website on the network, and developers use local servers to create websites before opening them to a wide range of users.
When entered into the address bar of the browser www.facebook.com A corresponding request is sent to the remote Facebook server. Once the browser receives the response, it interprets the code and displays the page.
Every time a user visits a page on the Internet, he interacts with the remote server's API. The API is the component part of the server that receives requests and sends responses.
API as a way to serve clients
Many companies offer APIs as a ready-made product. For example, Weather Underground sells access to its weather data API.
Usage scenario: On the website of a small company there is a form for making appointments for clients. The company wants to integrate Google Calendar into it to give customers the ability to automatically create an event and enter details about an upcoming meeting.
API Application: The goal is for the site server to directly contact the Google server with a request to create an event with the specified details, receive Google's response, process it, and send the appropriate information to the browser, for example, a confirmation message to the user.
Alternatively, the browser can make a request to Google's server API without going through the company's server.
How is the Google Calendar API different from the API of any other remote server on the network?
Technically, the difference is in the format of the request and response. To generate a full web page, the browser expects a response in HTML markup language, while the Google Calendar API will simply return data in a format like JSON.
If a request to the API is made by the server of a company's website, then it is the client (just as the browser is the client when the user opens the website).
Thanks to the API, the user gets the opportunity to perform an action without leaving the company’s website.
Most modern websites use at least a few third-party APIs. Many tasks already have ready-made solutions offered by third-party developers, be it a library or a service. It is often easier and more reliable to resort to a ready-made solution.
Many developers distribute the application to several servers, which interact with each other using the API. Servers that perform a supporting function to the main application server are called microservices.
So, when a company offers an API to its users, it simply means that it has created a series of special URLs that return only data as a response.
Such requests can often be sent through a browser. Since HTTP data transfer occurs in text form, the browser will always be able to display the response. For example, through a browser you can directly access the GitHub API (https://api.github.com/users/petrgazarov), without an access token, and receive this response in JSON format:
The browser perfectly displays the JSON response, which can be inserted into the code. It is easy enough to extract data from such text to use it at your discretion.
Some more API examples
The word "application" can have different meanings. In the context of the API, this means:
- a piece of software with a specific function,
- the entire server, the entire application, or just a separate part of the application.
Any piece of software that can be clearly distinguished from the environment can replace the letter “A” in an English abbreviation, and can also have some kind of API. For example, when a developer implements a third-party library into the code, it becomes part of the entire application. As a standalone piece of software, the library will have some kind of API that allows it to interact with the rest of the application code.
In object-oriented design, code is represented as a collection of objects. In an application, there can be hundreds of such objects interacting with each other. Each of them has its own API - a set public properties and methods for interacting with other objects in the application. Objects may also have private, internal logic that is hidden from the environment and is not an API.
Declare Function name Lib "libname" [()]
The Lib keyword specifies in which library Visual Basic can find the required function. This refers to dynamic link libraries (*.dll). But there is no need to specify the extension in aliasname. Alias specifies under what name the program should look for a given function in the library. Arglist is the passed parameters. The Windows API allows two things: carrying out certain tasks and accessing system resources. You can view a list of various API functions and their declarations using the standard API Viewer program.
Windows APIs can be called from Visual Basic to perform tasks for which standard Visual Basic code is not sufficient. For example, the standard Visual Basic tools do not allow you to restart your computer. However, a reboot can be performed by calling the appropriate Window API function.
Note: If an API function expects a variable from you, you must Necessarily declare it and fill it with spaces. Those. the variable must be user defined. These are features of the C++ language, in which the Windows API was written.
Let's look at a couple of examples:
Let's say your application needs to determine the directory where the Windows 95/98/NT operating system is installed. The easiest way to do this is to use the GetWindowsDirectory API function.
1. In the module we declare the GetWindowsDirectory API function:
3. In the Main subroutine we enter:
| Code |
| "The variable that needs to be passed to the API, we have already “we announced and now we fill in the blanks. "There should be approximately as many spaces as "approximately how many characters should the variable have. "In this case, 20 will be enough, since Windows is usually installed in " C:\Windows or C:\Win95, etc. That is, the sum of characters is more likely "the total will not exceed 20 WinDir = Space(20) Debug.Print Left(WinDir, GetWindowsDirectory(WinDir, 20)) "Since the API is a function, it should return some kind of "value. In this case, the GetWindowsDirectory function returns "the length of the sought value. That is, if, for example, the sought value " this is C:\WINDOWS, then the function will return the value 10. "The variable has a length of 20. These 10 characters are written "first, and then there are 10 spaces. Why do we, one might ask, "extra 10 characters? After all, this is using unnecessary memory... "Therefore, with the Left instruction we pull out from the WinDir variable "exactly as many first characters as are generally needed... |
Second example:
For example, your program must determine which of your media is CD-ROM or remote, etc. The "native" Visual Basic toolkit does not allow you to do this - you have to resort to the GetDriveType API function.
1. In the module we declare the GetDriveType API function:
2. In the Main subroutine we enter:
This is what the GetDriveType function will return to us, for example, for me:
A: - 2
C: - 3
D: - 3
E: - 5
All other letters are marked with the number 1. Yes, to understand these designations you need to know the following table:
Constant name and value:
DRIVE_UNKNOWN 0
DRIVE_NO_ROOT_DIR 1
DRIVE_REMOVEABLE 2
DRIVE_FIXED 3
DRIVE_REMOTE 4
DRIVE_CDROM 5
DRIVE_RAMDISK 6
The Main subroutine in the module is like Form_Load on the form, i.e. is considered the main one and is loaded by default. Back
The purpose of many API functions can be easily guessed by their names. For example, GetWindowsDirectory (get the Windows directory) or GetDriveType (get the media type).
Answer taken from: www.mtsecurity.narod.ru
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An API is an external interface for programming an application, accessing sites using a specific protocol to obtain information and simplified development of programs associated with internal services.
What does API mean?
The simplest analogy for using an API would be to use a calculator to perform complex calculations. Let's say you have a task, you can understand its essence, build equations and graphs, but you do not know how to perform arithmetic operations with numbers. There is a calculator next to you that can do these operations with ease. You don't know what's going on inside the computer, and you don't need to know. You give information in one form, and receive it in another, necessary for your purposes.
Any API works on this principle. You don’t care how the program gets the answer, what path the request takes inside it, how the calculations are performed. You are sure of only one thing - in response, standardized information will be given about the success of the operation or its error.
The API interface allows you not to waste your time, money and effort on buying a “new bike”. You get a working information port that receives and sends the necessary amounts of data for the purposes of your development.
Pros:
- Saving on developing your own interface.
- There is no need to understand the nuances of the issue.
- APIs are developed by professionals and take into account all the factors of internal processes that you may not be aware of when creating your solution.
- Allows you to communicate with services that are closed through other protocols.
Minuses:
- If the target service is updated, the API does not always immediately receive full functionality.
- You can't catch errors and don't know how the process works in someone else's code.
- The API does not always give the most optimized result in terms of time, since it is designed to handle general cases, not specific ones.
API Examples
API integration is the process of connecting an application to an external data interface. Working with the API begins with studying the documentation and protocols used, and then directly integrating your program into the interface. Let's look at the most popular services that have their own API.
VKAPI
External interface for interaction of the popular social network VKontakte with clients, as well as with browser and server applications. Allows you to manage community messages, group covers, user pages if you have the appropriate access keys.
All requests are made to the address https://api.vk.com/method/
After the slash comes the name of the API method used and the GET parameters of the request are transmitted. The response also comes via HTTPS in JSON format.
TELEGRAM BOT API
One of the most popular APIs. It is used to control bots in the Telegram messenger. After creating a bot via @botfather and obtaining the necessary access keys, you can begin interacting with the backend.
Requests can be made to: https://api.telegram.org/bot0000000:token/
Where bot0000000 is replaced by the unique identifier of your bot, and token expresses the secret key.
Requests are sent via HTTPS connections, the method name is indicated with a slash to the main address. The response comes in JSON format.
OPEN WEATHER MAP API
It is often necessary to obtain weather information without using third-party widgets and paid applications. The OpenWeatherMap service comes to the rescue with an open and free API. After registering and receiving identification data, you can send weather requests from server scripts around the world. In response to the city ID, the resource returns the most detailed information about the current weather and gives a forecast for the near future.
Format: HTTP transmission via api.openweathermap.org/data/2.5/weather?id= indicating the identification number of the desired city. Server response: JSON.
GOOGLE MAPS API
What could be nicer than an interactive world map on a website? Especially if this is not a template insert from Google Maps, but your personal edition of a popular map with personal clusters of markers. The map will interact with other scripts on the site, sending information about clicks and coordinates.
The Google Maps JavaScript API offers similar capabilities. The module is completely scripted and works on the browser side, so we don’t need HTTP requests from PHP and the formation of headers on the server side, as was the case in other APIs.
For example, placing a marker on a map will look like this:
var mark = new google.maps.Marker((
position: myPOS,
map: map,
title:"Hello!"
});
What is the need and benefits of using the API?
There are quite a lot of useful functions.
First aspect
You can establish interactive user interaction with social networks and instant messengers, use the capabilities of third-party computing systems to display exchange rates, weather and other important information.
Using the API, you can instantly connect other resources and software solutions to servers, which would normally take weeks of development. The API simplifies life where a unique implementation is not needed, and reliability and security are a priority.
Second aspect
If you are the owner of complex computing power, a popular service or data storage for public or semi-private access, then a good move would be to raise your own API. What will it give:
- Large flow of clients.
- Simplified access to your services for partners.
- Convenience of statistical analysis of service use.
Third aspect
Almost the same as the second one. But without having to implement an open access API. If you have a portal and want to create a mobile application for it on Android/IOS, then rewriting the system under a single API is the best solution. The entire data structure is systematized. The site and application will operate through single data channels.
Working with APIs can be both rewarding and frustrating. On the one hand, by interacting with other applications, you can greatly increase the audience reach and “wow” effect of your application. On the other hand, this involves reading tons of documentation, studying authentication strategies, and parsing uninformative (or even missing) error messages.
First of all, if you still don't fully understand what an API (Application Programming Interface) is, read Skillcrush's explanation and then the first part of this article to catch up.
"API" is an incredibly broad concept - every time your application "talks" to another application, it does so through some kind of API. Components within your own application, like different parts of Rails, also talk to each other through APIs. They are more or less independent sub-applications that provide the data each of them needs to perform their own specific tasks. In the app world, everything is an API!
When you build applications with more dynamic front-end functionality (both single-page Javascript applications and simple applications with individual AJAX calls), they will communicate with the Rails backend through your own API, which is really just an extra line or two of code , telling your controllers how to serve JSON or XML instead of HTML.
In this tutorial you will learn how to create your own API. In subsequent lessons we will cover how to interact with the APIs of other applications. The lessons should be a good springboard for learning about this topic, but are unlikely to fully cover all cases. A big part of working with APIs is knowing how to read their documentation and figure out what they want from you.
Points to Consider
Review the questions and see if you know the answers. Test yourself again after completing the task.
- How Rails understands what type of file you are expecting in response when you send an HTTP request.
- What is the purpose of the #respond_to method?
- How do you return a User object while specifying the attributes you don't want included in that object (that is, you can't just return User.first)?
- Name the 2 steps behind the scenes of the #to_json method.
- How do you tell a controller action to only render an error message?
- How to create your own error message?
- Why can't you use session-based controller authentication methods if you want to allow programmatic connections to your API?
- What is "Service Oriented Architecture"?
API Basics
Your Rails application is actually already an API, although you might not think of it as an API. The web browser your users launch is also a program, so it actually makes an API request to your Rails application when the user opens a new page. We tend to think this way because rendering HTML templates is such a common task that we simply bake this functionality into our server programs as a standard response type, and consider everything else to be something unusual.
However, often you want to make a request that doesn't require you to go through all the headaches of using a browser. You may not care about the page structure (HTML), but in return you want clean data. Let's say you want to get a list of all users. You can request something like http://yourapplication.com/users , which will surely trigger the #index action and render a list of all the app's users.
But why bother with all this extra information if all you want is a list of users? The simplest option would be to send a request to the same URL and expect a JSON or XML response in return. If you configure your Rails controller correctly, you will get back a simple JSON array object containing all the users. Wonderful!
The same principle applies when you communicate with an external API. Let's say you want to get a user's recent tweets from Twitter. All you need to do is tell your Rails application how to interact with Twitter's API (i.e., authenticate itself), send the request, and process the set of "tweets" that will be returned.
Creating an API
You might want to make your Rails application a pure backend API for frontend web pages, or you might just want to learn how to send JSON when the frontend requests it. This section will not cover how to create full-fledged RESTful APIs with authentication functions. This is a smooth introduction to treating your application as an API.
Basics
If you want your Rails application to return JSON instead of HTML, you will need to tell your controller to do so. The great thing is that the same controller action can return different types depending on whether your user is making a regular request from the browser or accessing the API via the command line. This determines what type of request was made based on the extension of the requested file, such as example.xml or example.json.
You can check what Rails thinks about the file type you expect by checking the server log:
Started GET "/posts/new" for 127.0.0.1 at 2013-12-02 15:21:08 -0800 Processing by PostsController#new as HTML
The first line tells you what URL was requested, and the second tells you where it was sent and how Rails processes it. If you were to use the .json extension it would look like this:
Started GET "/posts.json" for 127.0.0.1 at 2013-12-04 12:02:01 -0800 Processing by PostsController#index as JSON
If you have a test application running, try requesting different URLs. If your controller can't handle them, you might get an error, but you should still be able to see what Rails understands your requests to be.
Rendering JSON or XML
Once you decide that you want to respond to requests using JSON or XML, you will need to tell your controller to render JSON or XML instead of HTML. One way to do this is to use the #respond_to method:
Class UsersController< ApplicationController def index @users = User.all respond_to do |format| format.html # index.html.erb format.xml { render xml: @users } format.json { render json: @users } end end end
In this case, #respond_to passes a format object to the block, to which you can attach a corresponding render call. If you do nothing, the html will be rendered using the standard Rails template (in this example app/views/index.html.erb).
The #render function is smart enough to understand how to render a wide range of formats. When you pass it the key:json , it will call #to_json on the value, in this example @users . This will convert your Ruby object(s) into JSON strings that will be passed to the requesting application.
This way you get your API. Of course, creating an API can be a little more complex if you want to do some fancy things, but it all sticks to the basics.
Specifying Returned Attributes
Let's say you want to make sure you don't return the user's email address along with the User object. In this case, you will want to change the attributes that will be returned, modifying what the #to_json method does.
Previously, you would have simply overridden the #to_json method with your version, but now you won't need to - in fact, you will instead override the #as_json method. The #as_json method is used in the #to_json method, so its modification implicitly changes the result of #to_json , but in a rather specific way.
#to_json does 2 things: it runs #as_json and gets a hash of the attributes that will be rendered into JSON. It then renders to JSON using ActiveSupport::json.encode . So by modifying #as_json you are being more specific about the part of the #to_json method that you actually want to change.
In our case, we do this by modifying #as_json in our model to return only the attributes we need:
# app/models/user.rb class User< ActiveRecord::Base # Вариант 1: Полное переопределение метода #as_json def as_json(options={}) { :name =>self.name ) # DO NOT include the email field end # Option 2: Use the standard method #as_json def as_json(options=()) super(only: [:name]) end end
Then, our controller will just need to render the JSON as usual (in the example below, JSON will always be returned, regardless of whether an HTML request was sent or not):
# app/controllers/users_controller.rb class UsersController< ApplicationController def index render json: User.all end end
Note that you don't need to call #to_json yourself when you use #render - it will do this for you.
Sometimes Heroku may require additional steps to properly display your error pages. Take a look. You may need to remove static pages from the app/public directory first.
Ensuring security from outside
Let's say you want to allow access to the API only if the user is logged in. Your existing authentication in the controller already does this job - just make sure you have the correct #before_action set (e.g. before_action:require_login). You may need functionality where both logged-in and non-logged-in users can view the page, but each should see different data. You don't want unauthenticated users to be able to make API calls to get sensitive data. Likewise, you don't want to allow unauthorized users to visit certain HTML pages.
If you want to process requests from an application that is not a browser (for example, from the command line), you cannot rely on browser "cookies" for authentication. This is why most APIs use native tokens as part of the authentication process. We'll talk a little more about tokens in the next lesson.
Next steps
You now have the skills to use your Rails application to render not only HTML, but any other format as well. If you want to go further and allow other developers to build things using your platform (for example, so they can make programmatic requests instead of authenticating as a user), you will need to make your API system much more robust. We won't cover it all here, but check out the following:
- The article Building Awesome Rails APIs describes many of the best approaches for moving from a toy application towards industrial API standards.
Service-oriented architecture
It's time to introduce an architectural approach called Service-Oriented Architecture (SOA). The basic idea is that your application will consist of many services, such as a payment system, user registration, recommendation module, etc. Instead of building it all inside one main application, you break the subsystems into completely independent pieces that communicate with each other using internal APIs.
This is good for many reasons. Because each piece of your application doesn't care about how other parts work and only knows how to request data through their API, you can make significant changes to the service code and the rest of the application will work as before. You can completely replace one service with another, and as long as it communicates using the same API methods, it will go very smoothly. You can use external APIs as part of your application (eg payment systems) instead of writing your own. You can create a PHP application that communicates with a Python application that communicates with a Rails application, and everything will work because they communicate with each other using an API.
It's generally a good idea to try to make each part of your application as independent as possible. The concept of SOA forces you to think in terms of what methods you want to expose to other parts of your application, which will also make your code better. In addition, by assuming that each major component of your application is independent, you will also be able to isolate problems much more easily and handle errors in a more meaningful way.
Using a service-oriented architecture for an entire application is like breaking up a giant, complex Ruby script into neat classes and methods, only on a larger scale.
One of the most famous cases of transition to service-oriented architecture is Amazon.com. One day in 2002, Jeff Bezos bluntly stated that all workgroups must move to SOA or be fired. Notorious blog post Google employee, intended for internal purposes but accidentally made public, talked about the power of Amazon using SOA. It's a great read, so be sure to check it out, but the main points of Bezos' letter are summarized in the following quotes from the post:
1) All teams now provide their data and functionality through service interfaces.
2) Teams must communicate with each other through these interfaces.
3) Other forms of interprocess communication are prohibited: no direct links, no direct reading of another command's data, no shared memory models, no backdoors, etc. The only allowed way of interaction is to access the service interface over the network.
4) It doesn't matter what technology they use. HTTP, Corba, Pubsub, proprietary protocols - no difference. Bezos doesn't care.
5) All service interfaces, without exception, must be initially designed with the ability to be controlled externally. That is, the team must plan and design to be able to provide the interface to developers outside the company. No exceptions.
6) Anyone who ignores these requirements will be fired.
SOA is serious business. Sure, there are a lot of problems that come up when using it - check out this post about Amazon's "lessons learned" - but it has an incredible amount of benefits.
You probably won't worry too much about SOA while you're building toy apps for yourself, but it's definitely an issue that will come up when you start working for an IT company, so familiarizing yourself with it is a good practice.
Your aim
- Read Section 7 of the Rails Controllers Guide to learn about JSON and XML rendering.
- They're not required viewing (because they go a little further than we're currently prepared for), but if you're interested, take a look at Railscasts in the Additional Resources section at the bottom of the lesson to learn more about the benefits of the API.
Conclusion
We'll work more closely with your application as an API during the Javascript course. In this course, you'll create several full-stack applications that use AJAX calls for a better user experience, which essentially involves rendering XML or JSON data instead of a full HTML page. You'll then create several single-page Javascript applications that rely on the API provided by your Rails application to fetch all the necessary data from the database, but otherwise run on the client side (in the browser).
The best way to understand an API is to create and interact with it, which is what we will focus on in our projects.
Greetings!
In this article we will look at what an API is, where, how and for what it is used. We will also look at how the API can be used in your web developments and how it can simplify the life of a web programmer.
So let's start with the definition. API (Application Programming Interface) is a programming interface, an interface for creating applications. In more understandable terms, an API is ready-made code to make a programmer’s life easier. The API was created so that a programmer could actually make the task of writing an application easier by using ready-made code (for example, functions). The well-known jQuery, written in JavaScript, is also a kind of API. If we look at this example specifically, jQuery makes writing code much easier. What could be done using regular JavaScript tools in 30 lines is written in 5-6 using jQuery. If we look at APIs in general, we can find a lot of services that provide development solutions. The most famous today is the code.google.com service, which provides about fifty different APIs! This includes an interface for creating Android applications, various APIs for working with AJAX, and various application APIs that can be easily customized to your liking.
After all, does it make sense to write code yourself? Why work on what has already been created? Does it make sense to refuse free solutions (and in fact, free help) in web development? If you answered “NO” to all these questions, then consider that you understand the essence of the API.
But I also want to make a reservation. Beginner developers should NOT use half-baked solutions, as they will not cope with the real problem in the future. Therefore, if you are a beginner web programmer, then do not use semi-finished products! Learn to think with your own head, build various algorithms to understand the essence of programming. I also say, already addressing everyone, that APIs are not ready-made solutions, they are an environment, an interface for creating your own projects. You don't eat frozen cutlets from the store, do you? You fry them first, right? This analogy captures the essence of the API very clearly.
In general, I told you what an API is, where and how it is used, and most importantly, why. I wish you a pleasant learning of web programming and understanding its ever greater depths!
Tags: api
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