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| author | Misko Hevery | 2011-04-29 15:18:27 -0700 | 
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| committer | Igor Minar | 2011-06-06 22:28:38 -0700 | 
| commit | 11e9572b952e49b01035e956c412d6095533031a (patch) | |
| tree | 04dbf96802f552693d44c541c0d825a2769e3d57 /docs/content/guide/overview.ngdoc | |
| parent | b6bc6c2ddf1ae1523ec7e4cb92db209cd6501181 (diff) | |
| download | angular.js-11e9572b952e49b01035e956c412d6095533031a.tar.bz2 | |
Move documentation under individual headings
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| diff --git a/docs/content/guide/overview.ngdoc b/docs/content/guide/overview.ngdoc new file mode 100644 index 00000000..61c58435 --- /dev/null +++ b/docs/content/guide/overview.ngdoc @@ -0,0 +1,337 @@ +@ngdoc overview +@name Developer Guide: Overview +@description + + +* <a href="#H1_1">What Is Angular?</a> +* <a href="#H1_3">The Angular Philosophy</a> +* <a href="#H1_2">Anatomy Of An Angular App</a> +* <a href="#H1_4">Why You Want Angular</a> +* <a href="#H1_5">Angular's Ancestors</a> +* <a href="#H1_6">Watch a Presentation About Angular</a> + + +<a name="H1_1"></a> +# What Is Angular? + +The short answer: angular is a new, powerful, client-side technology that makes it much easier for +you to create dynamic web sites and complex web apps, all without leaving the comfort of your HTML +/ JavaScript home. + +The long answer: it kind of depends on where you're coming from... + +* If you're a web designer, you might perceive angular to be a sweet   {@link guide.template +templating} system, that doesn't get in your way and provides you with lots of nice built-ins that +make it easier to do what you want to do. + +* If you're a web developer, you might be thrilled that angular functions as an excellent web +framework, one that assists you all the way through the development cycle. + +* If you want to go deeper, you can immerse yourself in angular's extensible  HTML {@link +guide.compiler compiler} that runs in your browser. This compiler teaches your browser new tricks. + +So then, angular's not just a templating system, but you can create fantastic templates with it; +angular's not just a web framework, but it has a very nice one; and angular's not just an +extensible HTML compiler, but it has one of those too.  Let's put it this way: angular includes +these parts along with some others; it evolved naturally from earlier occurrences of these forms; +and thus angular is something far greater than the sum of its parts. It sounds like... it's alive! + +## An Intro By Way of Example + +Let's say that you are a web designer, and you've spent many thous — erm, hundreds of hours +designing web sites.  But at this point, the thought of doing DOM updates, writing listeners, and +writing input validators, all to do something as simple as implementing a form!?  You either don't +want to go there in the first place or you've been there and the thrill is gone. + +You could even be muttering to yourself as you hack another callback, "This is like building my own +bike from scratch every time I want to ride to the store." But let's say a clever friend, who keeps +tabs on these sorts of things, told you to check out angular. + +So now here you are checking out angular, and here is a simple example. Note that it features only +the templating aspect of angular, but this should suffice for now to quickly demonstrates how much +easier life can be with angular: + +<doc:example> +<doc:source> + <h2>Bigg Bike Shop</h2> + <hr> + <b>Invoice:</b> + <br/> + <br/> + <table> +  <tr><td> </td><td> </td> +  <tr><td>Quantity</td><td>Cost</td></tr> +  <tr> +    <td><input name="qty" value="1" ng:validate="integer:0" ng:required/></td> +    <td><input name="cost" value="19.95" ng:validate="number" ng:required/></td> +  </tr> + </table> + <hr> + <b>Total:</b> {{qty * cost | currency}} + <hr> +</doc:source> +<!-- +<doc:scenario> + it('should show of angular binding', function(){ +   expect(binding('qty * cost')).toEqual('$19.95'); +   input('qty').enter('2'); +   input('cost').enter('5.00'); +   expect(binding('qty * cost')).toEqual('$10.00'); + }); +</doc:scenario> +--> +</doc:example> + +Go ahead, try out the Live Preview above.  "Well I _declare_! It's a fully functioning form, with +an instantly updating display, and input validation." Speaking of being declarative, let's walk +through the example and look at the angular-related lines to see what's going on around here. + +In line __2__ of the example, we let the browser know about the angular namespace: + +       2 <html xmlns:ng="http://angularjs.org"> + +This ensures angular runs nicely in all major browsers. + +In line __3__ we do two angular setup tasks inside a `<script>` tag: + +1. We pull in `angular.js`. +2. The angular {@link angular.directive.ng:autobind ng:autobind} directive tells angular to {@link +guide.compiler compile} and manage the whole HTML document. + +       3 <script src="file:///Users/krculp/angular.js/build/angular.min.js" ng:autobind></script> + +Lines __14__ and __15__ set up one side of angular's very cool two-way data binding, as well as +demonstrate some easy input validation: + +       14 Quantity: <input name="qty" value="1" ng:validate="integer:0" ng:required/> +       15 Cost: <input name="cost" value="199.95" ng:validate="number" ng:required/> + +These input widgets look normal enough, but consider these points: + +* Remember the `ng:autobind` directive from line 3?  When this page loaded, angular bound the names +of the input widgets (`qty` and `cost`) to variables of the same name.  Think of those variables as +the "Model" part of the Model-View-Controller design pattern. +* Note the angular directives, {@link angular.widget.@ng:validate ng:validate} and {@link +ngular.widget.@ng:required ng:required}. You may have noticed that when you enter invalid data or +leave the the input fields blank, the borders turn a plainly irritated red color, and the display +value disappears.  These `ng:` directives make it easier to implement field validators than coding +them in JavaScript, no?  Yes. + +And finally, the mysterious line #__19__: + +       19 Total: {{qty * cost | currency}} + +What's with the curly braces?  Those curly braces are your friend.  This notation, `{{ _expression_ +}}`, is a bit of built-in angular {@link angular.markup markup}, a shortcut that you use to display +data. The expression within curly braces gets transformed by the angular compiler into an angular +directive ({@link angular.directive.ng:bind ng:bind}).  The expression itself can be a combination +of both an expression and a {@link angular.filter filter}: `{{ expression | filter }}`. + +In our example above, we're saying, "Bind the data we got from the input widgets to the display, +multiply them together, and format the resulting number into something that looks like money." + + +<a name="H1_3"></a> +# The Angular Philosophy + +Angular is built around the belief that declarative code is better than imperative when it comes to +building UIs and wiring software components together, while imperative code is clearly the way to +go for expressing business logic. + +Not to put too fine a point on it, but if you wanted to add a new label to your application, you +could do it by simply adding text to the HTML template, saving the code, and refreshing your +browser (this here is declarative): + +<pre> +<span class="label">Hello</span> +</pre> + +Or, as In programmatic systems (like {@link http://code.google.com/webtoolkit/ GWT}), you would +have to write the code and then run the code like this: + +<pre> +var label = new Label(); +label.setText('Hello'); +label.setClass('label'); +parent.addChild(label); +</pre> + +That looks like, let's see, do some math, factor out the `<pre>`s, carry the one, ummm...  a little +bit of markup versus four times as much code. + +More Angular Philosophy: + +* It is a very good idea to decouple DOM manipulation from app logic. This dramatically improves +the testability of the code. +* It is a really, _really_ good idea to regard app testing as equal in importance to app writing. +Testing difficulty is dramatically affected by the way the code is structured. +* It is an excellent idea to decouple the client side of an app from the server side.  This allows +development work to progress in parallel, and allows for reuse of both sides. +* It is very helpful indeed if the framework guides developers through the entire journey of +building an app: from designing the UI, through writing the business logic, to testing. +* It is always good to make common tasks trivial and difficult tasks possible. + +Now that we're homing in on what angular is, perhaps now would be a good time to list a few things +what angular isn't: + +* It's not a Library. You don't just call its functions, although it does provide you with some +utility APIs. +* It's not a DOM Manipulation Library. angular uses jQuery to manipulate the DOM behind the scenes, +rather than give you functions to manipulate the DOM with yourself. +* It's not a Widget Library. There are lots of existing widget libraries that you can integrate +with angular. +* It's not "Just Another Templating System". A part of angular is a templating system. The +templating subsystem of angular is different from the traditional approach for these reasons: +   * It Uses HTML/CSS syntax: This makes it easy to read and can be edited with existing HTML/CSS +authoring tools. +   * It Extends HTML vocabulary: Angular allows you to create new HTML tags, which expand into +dynamic UI components. +   * It Executes in the browser: Removes the round trip to the server for many operations and +creates instant feedback for users as well as developers. +   * It Has Bidirectional data binding: The model is the single source of truth. Programmatic +changes to the model are automatically reflected in the view. Any changes by the user to the view +are automatically reflected in the model. + + +<a name="H1_2"></a> +# Anatomy Of An Angular App + +This section describes the parts of an angular app in more detail. + +## Templates + +{@link guide.template Templates} are the part of angular that makes it easy and fun to create the +UI for your web apps.  With angular's templates you can create a dynamic UI using only HTML and +CSS, but now you can add your own elements, attributes, and markup.  The angular compiler reads the +"angularized" HTML when your page loads, and follows the instructions in there to generate a +dynamic page for you.  This is the View part of MVC. "But wait there's more": since the compiler is +extensible, you can build your own declarative language on top of HTML! + +## Application Logic and Behavior + +Application Logic and Behavior, which you define in JavaScript, is the C in MVC. With angular you +write the logic (the controllers) for your app, but because angular takes care of reflecting the +state of the model in the view, you don't have to write listeners or DOM manipulators. This feature +makes your application logic very easy to write, test, maintain, and understand. + +## Data + +In an angular app, all of your data is referenced from inside of a {@link angular.scope scope}. +The scope is the data Model, the M in the MVC pattern. A scope is a JavaScript object that has +watcher functions that keep tabs on the data that is referenced from that scope. The data could be +one or more Javascript objects, arrays, or primitives, it doesn't matter.  What matters is that +these are all referenced by the scope. + +This "scope thing" is how angular takes care of keeping your data model and your UI in sync. +Whenever something occurs to change the state of the scope, angular immediately reflects that +change in the UI, and vice versa. + +In addition to the three components described above (the MVC bits), angular comes with a set of +{@link angular.service Services} that are very helpful for building web apps. The services include +the following features: + +* You can extend and add application-specific behavior to services. +* Services include Dependency-Injection, XHR, caching, URL routing, and browser abstraction. + +The following illustration shows the parts of an angular application and how they work together: + +<img class="left" src="img/angular_parts.png" border="0" /> + + +<a name="H1_4"></a> +# Why You Want Angular + +Angular frees you from the following pain: + +* **Registering callbacks:** Registering callbacks clutters your code, making it hard to see the +forest for the trees. Removing common boilerplate code such as callbacks is a good thing. It vastly +reduces the amount of JavaScript coding _you_ have to do, and it makes it easier to see what your +application does. +* **Manipulating HTML DOM programatically:** Manipulating HTML DOM is a cornerstone of AJAX +applications, but it's cumbersome and error-prone. By declaratively describing how the UI should +change as your application state changes, you are freed from low level DOM manipulation tasks. Most +applications written with angular never have to programatically manipulate the DOM, although you +can if you want to, knock yourself out. +* **Marshaling data to and from the UI:** CRUD operations make up the majority of AJAX +applications. The flow of marshaling data from the server to an internal object to an HTML form, +allowing users to modify the form, validating the form, displaying validation errors, returning to +an internal model, and then back to the server (gah!) creates a lot of boilerplate code. Angular +eliminates almost all of this boilerplate, leaving code that describes the overall flow of the +application rather than all of the implementation details. +* **Writing tons of initialization code just to get started:** Typically you need to write a lot of +plumbing just to get a basic "Hello World" AJAX app working. With angular you can bootstrap your +app easily using services, which are auto-injected into your application in a {@link +http://code.google.com/p/google-guice/ Guice}-like dependency-injection style. This allows you to +get started developing features quickly. As a bonus, you get full control over the initialization +process in automated tests. + + +<a name="H1_5"></a> +# Angular's Ancestors + +Where does angular come from? What events led to the inevitability of the appearance of something +like angular? + +## First There Was HTML + +HTML was initially designed long, long ago, in the great year of 1989, with the intention to create +a markup language for sharing scientific documents over the network. Yes, yes, certainly there was +SGML even before that, but it was so difficult that even esteemed scientists balked at using it. +Thankfully, Tim Berners-Lee saved all of us from that pain with his much friendlier HTML. +`<HTML><BODY>Thank You, TB-L!</BODY></HTML>`. + +## Then There Was JavaScript + +Fast forward to 1995: JavaScript was invented. This was done with the best of intentions!  But in +practice it initially served mainly to annoy Internet users with cheap effects that "enhanced" +static HTML documents. + +Fast forward to the mid 2000s, when a new breed of back-then-considered-rich web applications +started to appear on the web. These were built with HTML, JavaScript, and CSS, and featured less +annoying and more impressive effects. Can you recall the first time you saw apps like Gmail, or +Google Maps, and you couldn't believe everything that was going on in the browser? + +## And JavaScript Prevailed + +As of this writing, in 2011, people are building still richer and more interactive web applications +that often rival their desktop counterparts. And yet they are essentially still working with +technology and programming primitives that were used decades ago for the creation of static +documents with cheap graphic effects. At the same time, the web is HUGE now, and we +can't just abandon the technologies it was built with. Applets, Flash and Silverlight tried it, and +in some ways succeeded. Yet many would argue that in reality they failed, because they tried to +work _around_ the web instead of working _with_ it. + +## And Then There Was Angular + +Angular recognizes the strengths of the existing "static" web technologies, as well as their +deficiencies.  At the same time, angular is learning from the failures of other technologies that +tried, or are trying, to work around the web. + +For these reasons angular plays to the strengths of established web technologies, instead of +bypassing them. Angular sets out the goal of increasing the abstraction and programming primitives +that developers use to build web applications, so as to better reflect the needs of modern web +applications and their developers. + + +<a name="H1_6"></a> +# Watch a Presentation About Angular + +Here is an early presentation on angular, but note that substantial development has occurred since +the talk was given in July of 2010. + +<object width="480" height="385"> + <param name="movie" value="http://www.youtube.com/v/elvcgVSynRg&hl=en_US&fs=1"></param> + <param name="allowFullScreen" value="true"></param> + <param name="allowscriptaccess" value="always"></param> + <embed src="http://www.youtube.com/v/elvcgVSynRg&hl=en_US&fs=1" +        type="application/x-shockwave-flash" allowscriptaccess="always" +        allowfullscreen="true" width="480" height="385"></embed> +</object> + +{@link +https://docs.google.com/present/edit?id=0Abz6S2TvsDWSZDQ0OWdjaF8yNTRnODczazdmZg&hl=en&authkey=CO-b7oID +Presentation} +| +{@link +https://docs.google.com/document/edit?id=1ZHVhqC0apbzPRQcgnb1Ye-bAUbNJ-IlFMyPBPCZ2cYU&hl=en&authkey=CInnwLYO +Source} | 
