Intro to APIs

In this section we will introduce you to Application Programming Interfaces (or APIs)

In this tutorial we investigate:

• What is an API?

• API design

• API endpoints

• Web services

What is an API?

API stands for Application Programming Interface. An API is like a go-between, that carries messages between two people who are unable (or are unwilling) to meet each other. Examples of famous go-betweens are, waiters & waitresses, mediators & translators.

If you have two people that speak different languages like an English client & a French seller, the only way for them to communicate is by having an intermediary that knows both English & French. The intermediary will translate English to French & French into English. This will allow the English client & the French seller to communicate.

This translation layer from English to French & French to English is similar to the way an API behaves.

In the case of an API, the client will send the API a message in a certain format. In our example, the message sent contains a request: "GET me shoes". The API will take this message, translate it & communicate this message to the seller. This will allow the seller to (A) understand the message & (B) pass back, the shoes.

In this example, the request to "GET me shoes" is sent using a protocol known as HTTPS, this stands for Secure Hyper Text Transfer protocol. This is not especially important at this stage, but just to comment that 99% of all APIs will use HTTPS as a method of sending & receiving data.

Now we know what an API is, at a super high level, let's dig into the backend portion of the API. In our example this is the "seller side", the French person returning the shoes when requested.

API Design

When a third party software provider builds an API for you to use, they first must decide what their API is going to allow you to do.

In our example of the shoe seller, the API is allowing us to request shoes. The seller therefore must have (as a minimum) a list of the shoes that are on offer & that are saved somewhere. The seller also needs to tell the world that they can ask for these shoes using certain key words.

Step 1. Creating the list of shoes

To create the list of shoes, the seller must first setup a database of shoes.

The contents of our database of shoes, showing different shoe types

Step 2. Create API Endpoints & Documentation

After the list of shoes has been created, the Seller builds what are called API endpoints. API endpoints are a list of ways that an outside party can interact with the sellers list of shoes. The seller will publish a complete list of their endpoints along with API documentation that provide a description of what the API endpoints do. The documentation is key so that people know what features are offered by the API.

In the example above, there are two API endpoints that are offered:

• GET me shoes, this endpoint lets you request a list of shoes

• POST new shoe type, this endpoint lets you send a new shoe type that will be added to the list of shoes.

Notice, if you want to DELETE or UPDATE the list of shoes using the API, this is not possible, because these two features are not offered by the API.

Stripes API documentation & endpoints

Each API exposes different functionality via a list of endpoints. As you've seen APIs do certain things, such as get lists of shoes. In this section, we will take a look at a real world example, using Stripes API as an example.

Stripes API allows you to receive & manage payments from your customers. Stripes API is very extensive & offers API endpoints that cover authentication, balances, charges, invoices etc.

Reading Stripes API Documentation

Stripes complete API documentation is here. It is very long, however Stripe have built a search function that allows you to filter for just the bit of the API that you're interested in.

For example, if we wanted read what functionality Stripe offers in terms of invoices, we first need to check if Stripes API offers that functionality.

To do this, you can press Ctrl+F & search for "Invoices".

Clicking the link takes you to the Invoices section of the Stripe API.

The endpoints for invoices are listed on the right hand side of the screen. If you look down you can see there is an option to GET invoices.

Scrolling down the page, you can both a description of what this endpoint does & what data you can expect to get back from the API.

Now you know that if you were to ask Stripe to GET /v1/invoices Stripe would return you some data in the format displayed above. This data format is called JSON. We will dig more into what exactly is JSON in the next section.

What is a Web Service?

A Webservice is someone else's API that they made available for the public. Inside Dittofi you're able to connect to other third party APIs using the web services tab that is visible under the "tools" icon in the side panel.

In this section, you're able to connect to APIs like stripe & add the different API endpoints that these APIs make available. For example:

Onwards

Read our section on webservices to see how to connect to a free API available on the internet.