core-decorators.js

core-decorators.js是一个第三方模块，提供了几个常见的装饰器，通过它可以更好地理解装饰器。

（1）@autobind

autobind装饰器使得方法中的this对象，绑定原始对象。

import { autobind } from 'core-decorators';
class Person {
  @autobind
  getPerson() {
    return this;
  }
}
let person = new Person();
let getPerson = person.getPerson;
getPerson() === person;
// true

（2）@readonly

readonly装饰器使得属性或方法不可写。

import { readonly } from 'core-decorators';
class Meal {
  @readonly
  entree = 'steak';
}
var dinner = new Meal();
dinner.entree = 'salmon';
// Cannot assign to read only property 'entree' of [object Object]

（3）@override

override装饰器检查子类的方法，是否正确覆盖了父类的同名方法，如果不正确会报错。

import { override } from 'core-decorators';
class Parent {
  speak(first, second) {}
}
class Child extends Parent {
  @override
  speak() {}
  // SyntaxError: Child#speak() does not properly override Parent#speak(first, second)
}
// or
class Child extends Parent {
  @override
  speaks() {}
  // SyntaxError: No descriptor matching Child#speaks() was found on the prototype chain.
  //
  //   Did you mean "speak"?
}

（4）@deprecate (别名@deprecated)

deprecate或deprecated装饰器在控制台显示一条警告，表示该方法将废除。

import { deprecate } from 'core-decorators';
class Person {
  @deprecate
  facepalm() {}
  @deprecate('We stopped facepalming')
  facepalmHard() {}
  @deprecate('We stopped facepalming', { url: 'http://knowyourmeme.com/memes/facepalm' })
  facepalmHarder() {}
}
let person = new Person();
person.facepalm();
// DEPRECATION Person#facepalm: This function will be removed in future versions.
person.facepalmHard();
// DEPRECATION Person#facepalmHard: We stopped facepalming
person.facepalmHarder();
// DEPRECATION Person#facepalmHarder: We stopped facepalming
//
//     See http://knowyourmeme.com/memes/facepalm for more details.
//

（5）@suppressWarnings

suppressWarnings装饰器抑制deprecated装饰器导致的console.warn()调用。但是，异步代码发出的调用除外。

import { suppressWarnings } from 'core-decorators';
class Person {
  @deprecated
  facepalm() {}
  @suppressWarnings
  facepalmWithoutWarning() {
    this.facepalm();
  }
}
let person = new Person();
person.facepalmWithoutWarning();
// no warning is logged