Angular2 forEach无法读取属性

Question

如何this.firms在数据中调用forEach()？

我知道如何在Angular1中执行此操作,但不知道我在Angular 2中的当前项目.

目前它在forEach之外工作正常,但不在内部.

 console.log(this.firms[0].name); // works
    var a = 0;
        console.log("--------------");

    data.forEach(function (eachObj) {
      console.log("firms check!");
      console.log(this.firms); // not working
      a = a + eachObj.income; 
      eachObj.name = this.firms[data.firmid - 1].name; // wont work
    });

错误:

Cannot read property 'firms' of undefined

Answer 1

上下文this不会被注入的匿名函数注入forEach().这this就是未定义的原因.

您可以使用arrow function,如果你正在使用ES6的特性,因为它使在功能的背景下:

data.forEach(eachObj => {
  console.log("firms check!");
  console.log(this.firms);
  a = a + eachObj.income; 
  eachObj.name = this.firms[data.firmid - 1].name;
});

或者直接绑定上下文:

data.forEach(function (eachObj) {
  console.log("firms check!");
  console.log(this.firms);
  a = a + eachObj.income; 
  eachObj.name = this.firms[data.firmid - 1].name;
}.bind(this));

编辑:

正如zeroflagL所提到的,您可以简单地将上下文传递给forEach():

data.forEach(function (eachObj) {
  console.log("firms check!");
  console.log(this.firms);
  a = a + eachObj.income; 
  eachObj.name = this.firms[data.firmid - 1].name;
}, this);