Question

如何在ng2中实现此承诺方案？

export class MySpecializedClass
{
    myObject;

    constructor(
        private myService: MyService
    )
    {
        this.myObject = new MyObject();
    }

    buildMyObject()
    {
        this.builderMethod1();
        this.builderMethod2();
    }

    builderMethod1()
    {
        this.myService.getData1()
    .then(response => this.myObject.Prop1 = response.Prop1 )
    }

    builderMethod2()
    {
        this.myService.getData2()
    .then(response => this.myObject.Prop2 = response.Prop2 )
    }
}

export class MyConsumerClass
{
    myObect;

    getMyObject()
    {
    this.myObject = new MySpecializedClass().buildMyObject().myObject;
    }
}

问题在于，在以下代码行中，在构建builderMethod1（）和builderMethod2（）之前，不应引用myObject。

MyConsumerClass.getMyObject().myObject

我希望builderMethod1（）和builderMethod2（）同时运行，这就是为什么它们没有在then（）中链接的原因。我怎么能用Promises实现这个场景？或者Observables或其他方法能提供更好的解决方案吗？

Answer 1

就我个人而言，我发现async-await语法比链接更具可读性。也许你也会这样，这就是使用async-await做同样的事情：

export class MySpecializedClass
{
    myObject : MyObject;

    constructor(
        private myService: MyService
    )
    {
        this.myObject = new MyObject();
    }

    async buildMyObject()
    {
        const first = this.builderMethod1();
        await this.builderMethod2();
        await first;
        return this.myObject;
    }

    async builderMethod1()
    {
        const response = await this.myService.getData1();
        this.myObject.Prop1 = response.Prop1;
    }

    async builderMethod2()
    {
        const response = await this.myService.getData2();
        this.myObject.Prop2 = response.Prop2;
    }
}

export class MyConsumerClass
{
    myObject;

    async getMyObject()
    {
        this.myObject = await new MySpecializedClass(new MyService()).buildMyObject()
    }
}

Answer 2

你可以回复承诺：

builderMethod2()
{
   return this.myService.getData2()
           .then(response => {
                 this.myObject.Prop2 = response.Prop2;
                 return response.Prop2;
             })
}

Answer 3

您可以在promise和Observable中执行此操作。我更喜欢可观察的，因为它有比承诺更多的选择

<强>许在承诺的情况下，您需要返回承诺/不同。但在你的情况下，你没有返回任何东西，当你说.then它解决了承诺

导出类MySpecializedClass { myObject的;

constructor(
    private myService: MyService
)
{
    this.myObject = new MyObject();
}

buildMyObject()
{
    var diff = differed // find out exact differed object
    return diff.all(this.builderMethod1(), this.builderMethod2());
}

builderMethod1()
{
     return this.myService.getData1()
.then(response => this.myObject.Prop1 = response.Prop1 )
}

builderMethod2()
{
    return this.myService.getData2()
.then(response => this.myObject.Prop2 = response.Prop2 )
}

}

导出类MyConsumerClass { myObect;

getMyObject()
{
 this.myObject = new MySpecializedClass().buildMyObject().then (() => {
   myObject;
 }
}

}

<强>可观察如果是可观察的，你可以Observable.merger，Observable.formJoin等加入你的2个观察者并订阅它们

如何在ng2中实现此承诺方案？

3 个答案: