"Encountering an undeclared variable issue within an Angular application that is built

I am attempting to assign values from a JSON response to some variables. However, when I try to retrieve and display these values using Console.log(), they are returning as "undefined."

Can anyone help me identify what mistake I might be making in this scenario?

public data: any;
carbs: string;
fat:any;
protein:any;

constructor(public navCtrl: NavController,public userprovider: UserProvider) {

    //fetches JSON array
    this.user = this.userprovider.getUser(userid);

    this.user.toPromise().then(res => {

        this.carbs = res[0].carbs;
        this.fat = res[0].fat;
        this.protein = res[0].protein;

    });

    console.log(this.carbs);
   //data assignment section
     this.data = {"Macros":[{"Macros":"Prot","time":this.protein,"color":"#3fa9f5","hover":"#57c0f5"},{"Macros":"Carb","time":this.carbs,"color":"rgb(236, 240, 241)","hover":"rgb(236, 240, 241)"},{"Macros":"Fat","time":this.fat,"color":"rgb(52, 73, 94)","hover":"rgb(52, 73, 94)"}]};


}

Answer №1

The reason for the issue is that console.log(this.carbs); is being called before this.carbs = res[0].carbs; is finished execution. To resolve this, it's recommended to call your function within the scope instead of outside.

Here's how you can update your code:

this.user.toPromise().then(res => {

        this.carbs = res[0].carbs;
        this.fat = res[0].fat;
        this.protein = res[0].protein;
			this.yourFunction(res[0].protein, res[0].carbs, res[0].fat );
    });

. . .

yourFunction(protein, carbs, fat){
 this.data = {"Macros":[{"Macros":"Prot","time":protein,"color":"#3fa9f5","hover":"#57c0f5"},{"Macros":"Carb","time":carbs,"color":"rgb(236, 240, 241)","hover":"rgb(236, 240, 241)"},{"Macros":"Fat","time":fat,"color":"rgb(52, 73, 94)","hover":"rgb(52, 73, 94)"}]};
}

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