Question

I have an application that uses Ajax.Request and its onSuccess event handler in lots of places.

I need to call a function (that will check the response) before all these onSuccess events fire. I tried using Ajax.Responders.register with onComplete event but it fires after Ajax.Request‘s onSuccess event. Any suggestions?

Answer 1

This might be a little late, but for the benefit of anyone else wondering about the same problem I will propose this solution:

You can use Prototypes own implementation of aspect-oriented programming to do this. Granted you will have to modify all your onSuccess-parameters, but it can be done with a simple search-and-replace, instead of updating all your callback functions. Here is an example Ajax.Request creation:

new Ajax.Request('example.html', {
    parameters: {action: 'update'},
    onSuccess: this.updateSuccessful
});

Say you have similar code snippets spread all over your code, and you want to preceed them all with a certain function that validates the response before the actual function is run(or even prevented from running at all). By using Funtion.wrap supplied in Prototype we can do this by extending the code above:

new Ajax.Request('example.html', {
    parameters: {action: 'update'},
    onSuccess: this.updateSuccessful.wrap(validateResponse)
});

Where ‘validateResponse’ is a function similar to this:

// If you use the X-JSON-header of the response for JSON, add the third param
function validateResponse(originalFn, transport /*, json */) {
    // Validate the transport

    if (someConditionMet) {
        originalFn(transport /*, json */);
    }
}

Thus you have extended your onSuccess-functions in one central place with just a quick search for onSuccess and pasting in ‘wrap(validateResponse)’. This also gives you the option of having several wrapper-functions depending on the needs of the particular Ajax-request.