How to get value of function that contains subscribe() method in ionic 2

Question

I'm trying to execute function after get the value of other function that contains firebase lists and subscribe method

no error in my code but I don't know why there is no value returned to the caller function.

This is a part of my typescript code

caller function

sendChat(chatT){
    if(this.checkPermission()){
        let myDate: String = new Date().toISOString();
        this.afd.list('/chats/').push({
            uid:this.userService.id,
            fname:this.userService.fname,
            lname:this.userService.lname,
            uemail:this.userService.email,
            text:chatT,
            time:myDate
        }).then(_=>{
            this.variables.chatText="";
        }).then(_=>{
            this.autoScroll();
        })
    }
}

returning function

checkPermission(){
    let check=false;
    this.permissionsList.take(1).subscribe(dataX=>{
        dataX.forEach(p=>{
            if(p.uemail==this.userService.email && p.type=="chat" && p.status==false){
                check=true;
                let alert = this.alertCtrl.create({
                    title: "Sending Failed",
                    subTitle: "You are not allowed to send any chats.",
                    buttons: ['OK']
                });
                alert.present();
            }
        })
        if(check==false){
            return true;
        }else{
            return false;
        }
    })
}

Note: these codes to define my firebase list

public permissionsList: FirebaseListObservable;

...

this.permissionsList = this.afd.list('/permissions/');

Answer 1

May it works for you

Use call back function to resolve it

checkPermission(callback){ 
   let check=false; 
   this.permissionsList.take(1).subscribe(dataX=>{ 
      dataX.forEach(p=>{ 
              if(p.uemail==this.userService.email && p.type=="chat" && p.status==false){ 
                check=true; 
                let alert = this.alertCtrl.create({ 
                                title: "Sending Failed", 
                                subTitle: "You are not allowed to send any chats.", 
                                buttons: ['OK'] 
                            }); 
                alert.present(); 
              } 
       }) 
    if(check==false){ 
      callback(true); 
    }else{ 
      callback(false); 
    } 
  }) 
}

And then

sendChat(chatT){ 
    if(this.checkPermission(function(data){ 
                                let myDate: String = new Date().toISOString();              
                                this.afd.list('/chats/').push({ uid:this.userService.id, fname:this.userService.fname, lname:this.userService.lname, uemail:this.userService.email, text:chatT, time:myDate }).then(_=>{ 
                this.variables.chatText=""; }).then(_=>{ this.autoScroll(); }) } }

Answer 2

Please take a look at the following code. I'm not sure if it'd work like it is, so please let me know if it throws any error so we can fix it:

public checkPermission(): Observable<any> {
    let check=false;

    return this.permissionsList
                .take(1)

                // Instead of subscribing to the observable, let's use the map
                // operator, so we can subscribe to it later in the caller method

                .map(dataX => {
                    dataX.forEach(p => {
                        if(p.uemail == this.userService.email && p.type == "chat" && p.status == false) {
                            check = true;
                            let alert = this.alertCtrl.create({
                                title: "Sending Failed",
                                subTitle: "You are not allowed to send any chats.",
                                buttons: ['OK']
                            });
                            alert.present();
                        }
                    });

                    // I've simplified this part :) 
                    return check === false;
                });
}

sendChat(chatT){

    // Call the method, and wait for the response
    this.checkPermission().subscribe(

        result => {

            // Now we get the result, let's check it
            if(result) {
                let myDate: String = new Date().toISOString();
                this.afd.list('/chats/').push({
                    uid:this.userService.id,
                    fname:this.userService.fname,
                    lname:this.userService.lname,
                    uemail:this.userService.email,
                    text:chatT,
                    time:myDate
                }).then(_=>{
                    this.variables.chatText="";
                }).then(_=>{
                    this.autoScroll();
                });
            }
        });
}

Answer 3

I could solve the problem by merge the 2 functions, But wish if there is any one can learn me how can I wait the returned value to use it for the longer codes

sendChat(chatT){
    let checkPer=false;
    this.permissionsList.take(1).subscribe(dataX=>{
        dataX.forEach(p=>{
            if(p.uemail==this.userService.email && p.type=="chat" && p.status==false){
                checkPer=true;
                let alert = this.alertCtrl.create({
                    title: "Sending Failed",
                    subTitle: "You are not allowed to send any chats. for any comments or explanations, you can contact us",
                    buttons: ['OK']
                });
                alert.present();
            }
        })
        if(checkPer==false){
            let myDate: String = new Date().toISOString();
            this.afd.list('/chats/').push({
                uid:this.userService.id,
                fname:this.userService.fname,
                lname:this.userService.lname,
                uemail:this.userService.email,
                text:chatT,
                time:myDate
            }).then(_=>{
                this.variables.chatText="";
            }).then(_=>{
                this.autoScroll();
            })
        }
    })
 }