this.serviceName.methodName().catch(err => {
  // Handle error here
  console.log("Something went wrong with the request, please try again.");

  // re-throw error so you can catch it when subscribing, fallback to generic error code
  return Observable.throw(err.message.toUpperCase() || 'API_ERROR');
}).subscribe((res) => {
    console.log(res);
});

this.serviceName.methodName().subscribe((res) => {
    console.log(res);
},
error=>{
  console.log(error);
});