Encountering issues arises when mixing synchronous and asynchronous code. The complexity is heightened due to having a variable accessed by external synchronous code within an asynchronous callback.
Analyze the behavior of the following example code.
function foo() {
var bar = false;
setTimeout(function () {
bar = true;
console.log(bar); // logs true
}, 1000);
console.log(bar); // logs false
return {
buzz: function () {
return bar;
}
};
}
// examine the output
var fizz = foo();
// immediate output
console.log(fizz.buzz()); // logs false
// .. wait for >1 second
setTimeout(function () {
console.log(fizz.buzz()); // logs true
}, 1500);
The setTimeout function in foo resembles the usage of .success or .error in your own code snippet.
So, what are the potential solutions to address this issue?
- Utilize the asynchronous callback to trigger subsequent code execution
- Emit an event from the callback and await that event before proceeding with other code segments (consider implementing custom event listeners/handlers based on your environment)
Here's an illustration for manually implementing events; it might be excessive for your requirements.
function ObjectWithEvents(obj) {
// Implementation details for event handling
}
ObjectWithEvents.prototype = Object.create(Object.prototype);
Incorporate the manual events feature into the foo example as follows:
function foo() {
// Functionality including asynchronous process
}
var fizz = foo();
fizz.addEventListener('load', function () {
console.log(fizz.buzz()); // logs true
});
This is a streamlined approach for integrating a callback within your existing code structure.
.factory('GCs', ['$http', function($http) {
// Definition of object and HTTP request
}]);
function code_needing_obj() {
// Code segment requiring the object obtained through HTTP request
}
You could even consider rearranging your code so that the HTTP call precedes all other operations.
// Ensure $http is defined here
$http.post("mydomina.com?myrequest=getbyid", { "id": "1"} )
.success(code_needing_obj)
.error(function(data, status, headers, config) {
// Error handling
});
function code_needing_obj(obj) {
// Segments relying on the fetched object data
}