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如何在typescript中修改promise内的变量(范围和“this”问题)?

promise typescript javascript

0

Sasha Grievus · 技术社区 · 7 年前

我已经使用typescript 2.2.1在ionic 4.5.0中建立了一个项目。

在它里面,我有两个班

file functions.ts
/* lots of import */
@Injectable()
export class Functions {
  language: string;
}

file fooclass.ts
/* lots of import and import of functions.ts */
export class FooClass {
   constructor(public functions: Functions) {
     this.functions.language="ENG";
   }

   somefunction() {
     console.log("1 - language: "+this.functions.language);
     this.someotherfunction().then((response) => {
        console.log("2 - language: "+this.functions.language);
     })
     console.log("3 - language: "+this.functions.language);
   }

someotherfunction() {
  return new Promise((resolve) => {
     this.functions.language="ITA";
     resolve("done");   
  }
}

这是打印出来的

1 - language: ENG
2 - language: ITA
3 - language: ENG

我认为使用胖箭头可以绑定'this'环境,以便对this.functions的变量'language'进行更改可以在其他函数的允诺中存活下来,但似乎不行。如何修改变量语言并使更改在承诺之外继续存在?

1 回复 | 直到 7 年前

1

0

Drew Reese 7 年前

functions

class FooClass {
  constructor() {
    this.language="ENG";
  }

  somefunction() {
    console.log("1 - language:" + this.language);
    this.someotherfunction()
    .then((response)=>{
      console.log("2 - language: " + this.language);
    });
    console.log("3 - language: " + this.language);
  }

  someotherfunction() {
    return new Promise((resolve) =>{
      this.language = "ITA";
      resolve("done");   
    });
  }
}

const foo = new FooClass();
foo.somefunction();

保存“函数”参数时,它也起作用:

class FooClass {
  constructor(functions) {
    this.functions = functions;
  }

  somefunction() {
    console.log("1 - language:" + this.functions.language);
    this.someotherfunction()
    .then((response)=>{
      console.log("2 - language: " + this.functions.language);
    });
    console.log("3 - language: " + this.functions.language);
  }

  someotherfunction() {
    return new Promise((resolve) =>{
      this.functions.language = "ITA";
      resolve("done");   
    });
  }
}

const foo = new FooClass({ language: "ENG"});
foo.somefunction();