如何在 Ionic 2 中等待值

Question

我正在尝试等待执行后可能会更改的值 "this.bookmarList.take(1).subscribe(..."

我的问题是，当我运行应用程序时，它会在执行我的订阅之前执行第二个 if 语句 "if(found==false)"。

这是我的代码，您可能会发现一些错误或需要添加一些补充来解决我的问题。

let loader = this.loadingCtrl.create({
  content: "",
});
let found=false;
loader.present().then(()=>{
    this.bookmarkList.take(1).subscribe(data=>{
        data.forEach(b=>{
            if(b.nID==this.appService.id && b.url==url){
                let alert = this.alertCtrl.create({
                title: 'Already Bookmarked',
                    subTitle: 'This note image already bookmarked',
                    buttons: ['OK']
                });
                alert.present();
                found=true;
            }
        })
    })
}).then(()=>{
    if(found==false){
        this.afd.list('/bookmark/').push({
            uemail: this.userService.email,
            nID: this.appService.id,
            url: url,
            date: dateX
        });
        let alert = this.alertCtrl.create({
            title: 'Bookmarked Successfully',
            subTitle: 'This note image has been bookmarked successfully',
                buttons: ['OK']
        });
        alert.present();
    }
}).then(_=>{
    loader.dismiss();
})

Answer 1

我能找到解决方案

let loader = this.loadingCtrl.create({
  content: "",
});
let found=false;
loader.present().then(_=>{
    this.bookmarkList.take(1).subscribe(data=>{
        data.forEach(b=>{
            if(b.nID==this.appService.id && b.url==url){
                let alert = this.alertCtrl.create({
                    title: 'Already Bookmarked',
                    subTitle: 'This note image already bookmarked',
                    buttons: ['OK']
                });
                alert.present();
                found=true;
            }
        })
        if(found==false){
            this.afd.list('/bookmark/').push({
                uemail: this.userService.email,
                nID: this.appService.id,
                url: url,
                date: dateX
            });
            let alert = this.alertCtrl.create({
                title: 'Bookmarked Successfully',
                subTitle: 'This note image has been bookmarked successfully',
                buttons: ['OK']
            });
            alert.present();
        }
        //return
    })
}).then(_=>{
    loader.dismiss();
})

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