Designing Good API and its importance Imran M Yousuf Entrepreneur Smart IT Engineering Ltd.

Why is API important?

Designing API

General Principles

OOP Design Principles Smart IT Engineering Ltd.

API is a source code-based specification intended to be used as an interface by software components to communicate with each other.

ABI (Application Binary Interface) differs to API in that the former is specified on binary interface

In this presentation we will consider ABI as API too Smart IT Engineering Ltd.

Do we integrate Facebook API (FB Login, Like, Share, etc.)? How?

How do we develop softwares that require system level integration?

How do Web 2.0 portals communicate with its server?

How do Smart Phone / Tablet Apps communicate with server? Smart IT Engineering Ltd.

A lot of (Almost all) websites integrate with FB using its JavaScript API

For Windows we use MFC or Windows API; for *nix system we use POSIX etc.

Web 2.0 / Smart Phone / Tablet Apps make server side calls via HTTP protocol either from a App or from browser using AJAX. Smart IT Engineering Ltd.

You are developing an Android or iPhone App and having problem using their API as you not understanding how to simply achieve them. What would you do?

Your client asked you to use a Web Service to integrate one service to another and the Web Service makes no sense what so over and furthermore, it does not have ample documentation. What would you do?

What would be your opinion of such API providers? Smart IT Engineering Ltd.

Contact Andoid community mailing lists/forums and ask there

Contact iPhone Developer Community and ask there

Ask my customer to get me documentation or ask the company/developer for help

We think those companies and their developers are crap and we are better than them Smart IT Engineering Ltd.

Cost to stop/change API can be prohibitive

Easy to use, even without documentation

Hard to misuse

Easy to read and maintain code that uses it

Sufficiently powerful to satisfy requirements

Easy to extend

Appropriate to audience Smart IT Engineering Ltd.

Designing API Smart IT Engineering Ltd.

At the very beginning agility trumps completeness

It serves as an API used by API implementations

If you write one, it probably won't support another

If you write two, it will support more with difficulty

If you write three, it will work fine Smart IT Engineering Ltd.

Aim to displease everyone equally

Expect to evolve API Smart IT Engineering Ltd.

General Principles Smart IT Engineering Ltd.

Good names enables API to thrive

Write tests demonstrating API usage

Specification will get more specific through usage Smart IT Engineering Ltd.

Public class should have no public fields other than constants

This maximizes information hiding

Allows modules to be used, understood, built, tested and debugged independently Smart IT Engineering Ltd.

Be regular – strive for symmetry

Code should read like prose Smart IT Engineering Ltd.

Do not wrap API to gain performance

Be aware of stateful vs stateless requirements Smart IT Engineering Ltd.

Prefer composition over inheritence

Provide programmatic access to all data available in string form to avoid user parsing strings Smart IT Engineering Ltd.

Use most specific possible input parameter type

Avoid using float (32 bits) in favor of double (64 bits) Smart IT Engineering Ltd.

Lon list of identically typed params is harmful

This presentation covered some heuristics of the craft

API design is tough

Once a API is Public it can evolve but has to support earlier releases Smart IT Engineering Ltd.

Questions? Smart IT Engineering Ltd.