Losing data while making API calls in Angular 4

In my Angular 4 project, I am making two API calls within the ngOnInit lifecycle hook. My goal is to pass the data received from the first API call to the second one.

However, when I try to access the value in the second API method, it returns as "Undefined".

Here's a snippet of my code:

ngOnInit() {

        this.http.get('https://api.ipify.org/?format=json').subscribe(
            data => {
                this.ip_Address = data['ip'];
                console.log(this.ip_Address);   
            },
            error => console.error(error)
        );

        this.http.get(`http://localhost:xyz/api/data/INSERT_USER_SESSION/?IP_Address=${this.ip_Address}&Time=${this.date_and_time}&state=${this.session_Begin_Status}`)
            .subscribe(data => this.res = data['']);
}

Although the IP Address is logged successfully in the console, it appears as "undefined" when passed to the second API call. Can someone please point out where I might have made a mistake?

Answer №1

One way to avoid errors is by checking the response code and data body before parsing the data and calling a second service. Another approach is to create separate functions and call them in your initialization process.

Answer №2

One issue arises when moving beyond a subscribe method, causing data from the service to become undefined. This can be observed in the console - data that was defined within the service becomes undefined once outside of the subscribe method. To address this, consider implementing a switchmap or similar solution. I encountered a similar problem and found a helpful discussion on Stack Overflow at this link. Another approach is to perform your second service within the context of your first service.

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