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https://github.com/silverstripe/silverstripe-framework
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267 lines
7.8 KiB
Plaintext
267 lines
7.8 KiB
Plaintext
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h1. Concrete - Support for ConcreteUI programming in jQuery
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A basic desire for jQuery programming is some sort of OO or other organisational method for code. For your consideration,
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we provide a library for ConcreteUI style programming. In ConcreteUI you attach behavioral code to DOM objects. Concrete extends this
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concept beyond what is provided by other libraries to provide a very easy to use system with class like, ploymorphic, namespaced properties
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h2. Basic use
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h4. First intro
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To attach methods to DOM nodes, call the `concrete` function on a jQuery selector object, passing a hash listing the method names and bodys
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<pre><code>
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$('div').concrete({
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foo: function(..){..},
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bar: function(..){..}
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});
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</code></pre>
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You can then call those methods on any jQuery object.
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<pre><code>
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$('#a').foo();
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</code></pre>
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Any elements in the jQuery selection that match the selector used during definition ('div' in this example) will have foo called with that element
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set as this. Any other objects are skipped. The return value will be the return value of foo() for the last matched DOM object in the set
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h4. A proper example
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Given this DOM structure:
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<pre><code>
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<body>
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<div class="internal_text">Internal text</div>
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<div class="attribute_text" rel="Attribute text"></div>
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<div>Nonsense</div>
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</body>
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</code></pre>
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And this concrete definition
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<pre><code>
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$('.internal_text').concrete({
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foo: function(){ console.log(this.text()); }
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});
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$('.attribute_text').concrete({
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foo: function(){ console.log(this.attr('rel')); }
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});
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</code></pre>
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Then this call
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<pre><code>
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$('div').foo();
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</code></pre>
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Will log this to the console
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<pre><code>
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Internal text
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Attribute text
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</code></pre>
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h4. Limitations
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When defining methods, the jQuery object that concrete is called on must be a plain selector, without context. These examples will not work
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<pre><code>
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$('div', el).concrete(...)
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$([ela, elb, elc]).concrete(...)
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$('<div id="a"></div>').concrete(...)
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</code></pre>
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h2. Live
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The definitions you provide are not bound to the elements that match at definition time. You can declare behaviour prior to the DOM existing in any
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form (i.e. prior to DOMReady) and later calls will function correctly.
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h2. Selector specifity
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When there are two definitions for a particular method on a particular DOM node, the function with the most _specific_ selector is used.
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_Specifity_ is calculated as defined by the CSS 2/3 spec. This can be seen as _subclassing_ applied to behaviour.
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Another example. Given this DOM structure
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<pre><code>
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<body>
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<div>Internal text</div>
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<div class="attribute_text" rel="Attribute text"></div>
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<div>Nonsense</div>
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</body>
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</code></pre>
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And this concrete definition
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<pre><code>
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$('div').concrete({
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foo: function(){ console.log(this.text()); }
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});
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$('.attribute_text').concrete({
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foo: function(){ console.log(this.attr('rel')); }
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});
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</code></pre>
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Then this call
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<pre><code>
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$('div').foo();
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</code></pre>
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Will log this to the console
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<pre><code>
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Internal text
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Attribute text
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Nonsense
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</code></pre>
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h2. Events
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If you declare a function with a name starting with 'on', then instead of defining that function, it will be bound to an event of that
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name. Just like other functions this binding will be live, and only the most specific definition will be used
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<pre><code>
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<head>
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<script type='text/javascript'>
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/* No need for onready wrapper. Events are bound as needed */
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$('div').concrete({
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onclick: function(){ this.css({backgroundColor: 'blue'}); }
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});
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$('.green').concrete({
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onclick: function(){ this.css({color: 'green'}); }
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});
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</script>
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<body>
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<div>Background will turn blue when clicked on</div>
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<div>Will also have blue background when clicked on</div>
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<div class='green'>Will have green text when clicked on. Background color will not change</div>
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</body>
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</code></pre>
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h2. Constructors / Destructors
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Declaring a function with the name `onmatch` will create a behavior that is called on each object when it matches. Likewise, `onunmatch` will
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be called when an object that did match this selector stops matching it (because it is removed, or because you've changed its properties).
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Note that an onunmatch block must be paired with an onmatch block - an onunmatch without an onmatch _in the same concrete definition block_ is illegal
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Like other functions, only the most specific definition will be used. However, because property changes are not atomic, this may not work as you
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expect.
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h2. Namespaces
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To avoid name clashes, to allow multiple bindings to the same event, and to generally seperate a set of functions from other code you can use namespaces
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<pre><code>
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$('div').concrete('foo.bar', function($){ return {
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baz: function(){}
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}});
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</code></pre>
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You can then call these functions like this:
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<pre><code>
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$('div').concrete('foo.bar').baz()
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</code></pre>
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Namespaced functions work just like regular functions (`this` is still set to a matching DOM Node). However, specifity is calculated per namespace.
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This is particularly useful for events, because given this:
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<pre><code>
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$('div').concrete({
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onclick: function(){ this.css({backgroundColor: 'blue'}); }
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});
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$('div').concrete('foo', function($){ return {
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onclick: function(){ this.css({color: 'green'}); }
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}});
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</code></pre>
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Clicking on a div will change the background **and** foreground color.
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This is particularly important when writing reusable code, since otherwise you can't know before hand whether your event handler will be called or not
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Although a namespace can be any string, best practise is to name them with dotted-identifier notation.
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h4. Namespaces and scope (or What the hell's up with that ugly function closure)
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Inside a namespace definition, functions remember the namespace they are in, and calls to other functions will be looked up inside that namespace first.
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Where they don't exist, they will be looked up in the base namespace
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<pre><code>
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$('div').concrete('foo', {
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bar: function() { this.baz(); this.qux(); }
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baz: function() { console.log('baz'); }
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})
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$('div').concrete({
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qux: function() { console.log('qux'); }
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})
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</code></pre>
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Will print baz, qux to the console
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Note that 'exists' means that a function is declared in this namespace for _any_ selector, not just a matching one. Given the dom
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<pre><code>
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<div>Internal text</div>
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</code></pre>
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And the concrete definitions
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<pre><code>
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$('div').concrete('foo', {
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bar: function() { this.baz(); }
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})
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$('span').concrete('foo' {
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baz: function() { console.log('a'); }
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$('div').concrete({
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baz: function() { console.log('b'); }
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})
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</code></pre>
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Then doing $('div').bar(); will _not_ display b. Even though the span rule could never match a div, because baz is defined for some rule in the foo namespace, the base namespace will never be checked
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h4. Forcing base
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In some situations (such as the last example) you may want to force using the base namespace. In this case you can call concrete without any arguments. For example, if the first definition in the previous example was
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<pre><code>
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$('div').concrete('foo', {
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bar: function() { this.concrete().baz(); }
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})
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</code></pre>
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Then b _would_ be output to the console. It is up to the developer to decide when they need to be explicit about using the base namespace
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h4. Using
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Sometimes a block outside of a namespace will need to refer to that namespace repeatedly. By passing a function to the concrete function, you can change the looked-up namespace
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<pre><code>
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$('div').concrete('foo', {
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bar: function() { console.log('a'); }
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})
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$('div').concrete('foo', function(){
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this.bar();
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});
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</code></pre>
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This equivilent to /with/ in javascript, and just like /with/, care should be taken to only use this construct in situations that merit it.
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