如何共享承诺链中的角服务？
提问于 2019-05-24 01:02:42
我正在写Angular6 (打字本)。我想用下面的代码把承诺联系起来.
public start() {
this.p1()
.then(this.p2)
.then(this.p3)
.catch((err) => console.log(err));
}
public p1(): Promise<string> {
return new Promise((resolve, reject) => {
this.httpService.sendHello().subscribe(response => {
resolve();
});
});
}
public p2(): Promise<string> {
return new Promise((resolve, reject) => {
this.httpService.sendHello().subscribe(response => {
resolve();
});
});
}
public p3(): Promise<string> {
return new Promise((resolve, reject) => {
this.httpService.sendHello().subscribe(response => {
resolve();
});
});
}但出现“无法读取未定义的属性'httpService‘”时出现错误。
如何在承诺链中共享angular6服务？
谢谢你的帮助，
回答 4
Stack Overflow用户
回答已采纳
发布于 2019-05-24 01:09:58
当不使用箭头函数时，类型记录不绑定this。
而不是then(this.p2)，您可以编写then(() => this.p2())
public start() {
this.p1()
.then(() => this.p2())
.then(() => this.p3())
.catch((err) => console.log(err));
}
public p1(): Promise<string> {
return new Promise((resolve, reject) => {
this.httpService.sendHello().subscribe(response => {
resolve();
});
});
}
public p2(): Promise<string> {
return new Promise((resolve, reject) => {
this.httpService.sendHello().subscribe(response => {
resolve();
});
});
}
public p3(): Promise<string> {
return new Promise((resolve, reject) => {
this.httpService.sendHello().subscribe(response => {
resolve();
});
});
}Stack Overflow用户
发布于 2019-05-24 01:06:15
将它作为函数的参数，如下所示：
public start() {
this.p1(this.httpService)
.then(this.p2)
.then(this.p3)
.catch((err) => console.log(err));
}
public p1(httpService: HttpService): Promise<string> {
return new Promise((resolve, reject) => {
httpService.sendHello().subscribe(response => {
resolve();
});
});
}Stack Overflow用户
发布于 2019-05-24 01:08:38
这是this上下文。将它们转换为箭头函数：
public p1 = (): Promise<string> => { //...页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/56289254
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