title: Angular - Make multiple HTTP calls sequentially
body: <p>I need to make a function to make HTTP calls sequentially inorder to use response of one call into other one like getting IP address of user from first call and use that IP to register user in second call. </p>
  
  <p>Demo code:</p>
  
  <pre><code>registerUser(user: User) {
      this.utility.getIpAddress()
      .subscribe(data =&gt; {
          this.ipAddress = data.ip;
      });
      const body = {
          UserName: user.UserName,
          Email: user.Email,
          //...
          UserIP: this.ipAddress,
      }
      return this.http.post(this.registerAPI, body);
  }
  </code></pre>