First of all, let's give an example: the example of you going to the bank to withdraw money. If there is no bank teller to serve you and you save money yourself, the things you need to do are:
1. Open the door of the vault
Two, put the money in
Three, keep accounts, how much money is deposited
Four, leave.
The problem is solved, but there are many problems. Everyone does this, four steps, some people can't open the door of the vault, and some people are illiterate and can't keep accounts. And also remember it wrong.
What to do, the bank hires a bank teller, her name is Xiaohua, that's fine. The bank teller is very clear about these four steps. The things you need to do now are:
1. Give the money to the bank teller Xiaohua
Two, leave
How about, the efficiency is greatly improved, and it is not easy to make mistakes.
The role of this bank teller is the role of API.
One day, a person came and said to Xiaohua, the bank teller, to apply for a card. Xiaohua looked dazed, never done it before, and didn't know the process. At this time, the bank hired a teller who could handle cards, Xiao Hong. Then between the bank and the customer, it is stipulated that what kind of business should be done well to find Xiaohua or Xiaohong, this stipulation is an agreement.
Another day, someone came and spoke English to Xiao Hua, asking for money. Xiaohua couldn't understand it, indicating that she couldn't do it. Xiaohua said, please speak Mandarin, OK? Mandarin, in the world of programming, is the format, usually composed of json and xml.
This document draws on a great god, the thief written is good, and I recommend it to everyone.
https://blog.csdn.net/cumtdeyurenjie/article/details/80211896
Programmers from all over the world unite!