dojo.partial¶
| Status: | Draft |
|---|---|
| Version: | 1.2 |
Have you ever wanted to control arguments being passed into a function? For example, have you ever had the need to set the first parameter of a function to a defined value and allow the others to still vary? Well, dojo provides a way to do that! Partial is a cousin to ‘hitch’ in that it’s a function that returns a function. What it does is allow you to fix the first N parameters of a function call to some specific value. This can be very powerful, especially when you want to pass in object references or the like into notification functions of DataStores.
Lets take a quick look at a pseudo-code example of using partial:
var dataLoaded = function(someFirstParam, data, ioargs) {};
var args = {
url: "foo",
load: dataLoaded
}
dojo.xhrGet(args);
Okay, so that will invoke the dataLoaded function when the xhrGet function returns ... but load of xhrGet expects param structure of: load(data, ioargs). So how the heck do we make sure that xhrGet's expectations are honored even with that new first param called 'someFirstParam'? Enter dojo.partial! Here's how you would do it:
var dataLoaded = function(someFirstParam, data, ioargs) {};
var args = {
url: "foo",
load: dojo.partial(dataLoaded, "firstValue");
}
dojo.xhrGet(args);
What that does is create a new function that wraps dataLoaded and affixes the first parameter with the value "firstValue". Note that dojo.partial allows you to do N parameters, so you can keep defining as many values as you want for fixed-value parameters of a function.
Basic Example¶
Let's look at a quick runnong example:
<script type="text/javascript">
dojo.require("dijit.form.Button");
dojo.addOnLoad(function() {
var myClick = function(presetValue, event) {
var node = dojo.byId("appendLocation");
node.appendChild(document.createTextNode(presetValue));
node.appendChild(document.createElement("br"));
}
dojo.connect(dijit.byId("myButton"), "onClick", dojo.partial(myClick , "This is preset text!"));
});
</script>
<button dojoType="dijit.form.Button" id="myButton">Click me to append in a preset value!</button>
<div id="appendLocation"></div>