diff --git a/aio/content/guide/architecture-next-steps.md b/aio/content/guide/architecture-next-steps.md index 10999c9e00..e44796d132 100644 --- a/aio/content/guide/architecture-next-steps.md +++ b/aio/content/guide/architecture-next-steps.md @@ -11,6 +11,8 @@ about the features and tools that can help you develop and deliver Angular appli ## Application architecture +* The [Components and templates](guide/displaying-data) guide explains how to connect the application data in your [components](guide/glossary#component) to your page-display [templates](guide/glossary#template), to create a complete interactive application. + * The [NgModules](guide/ngmodules) guide provides in-depth information on the modular structure of an Angular application. * The [Routing and navigation](guide/router) guide provides in-depth information on how to construct applications that allow a user to navigate to different [views](guide/glossary#view) within your single-page app. diff --git a/aio/content/guide/displaying-data.md b/aio/content/guide/displaying-data.md index e834530862..8229ed3e84 100644 --- a/aio/content/guide/displaying-data.md +++ b/aio/content/guide/displaying-data.md @@ -1,11 +1,20 @@ -# Displaying data +# Displaying data in views -You can display data by binding controls in an HTML template to properties of an Angular component. +Angular [components](guide/glossary#component) form the data structure of your application. +The HTML [template](guide/glossary#template) associated with a component provides the means to display that data in the context of a web page. +Together, a component's class and template form a [view](guide/glossary#view) of your application data. -In this page, you'll create a component with a list of heroes. -You'll display the list of hero names and -conditionally show a message below the list. +The process of combining data values with their representation on the page is called [data binding](guide/glossary#data-binding). +You display your data to a user (and collect data from the user) by *binding* controls in the HTML template to the data properties of the component class. +In addition, you can add logic to the template by including [directives](guide/glossary#directive), which tell Angular how to modify the page as it is rendered. + +Angular defines a *template language* that expands HTML notation with syntax that allows you to define various kinds of data binding and logical directives. +When the page is rendered, Angular interprets the template syntax to update the HTML according to your logic and current data state. +Before you read the complete [template syntax guide](guide/template-syntax), the exercises on this page give you a quick demonstration of how template syntax works. + +In this demo, you'll create a component with a list of heroes. +You'll display the list of hero names and conditionally show a message below the list. The final UI looks like this:
@@ -14,20 +23,14 @@ The final UI looks like this:
- - -The demonstrates all of the syntax and code -snippets described in this page. - +The demonstrates all of the syntax and code snippets described in this page.
- {@a interpolation} ## Showing component properties with interpolation -The easiest way to display a component property -is to bind the property name through interpolation. +The easiest way to display a component property is to bind the property name through interpolation. With interpolation, you put the property name in the view template, enclosed in double curly braces: `{{myHero}}`. Use the CLI command [`ng new displaying-data`](cli/new) to create a workspace and app named `displaying-data`. @@ -39,63 +42,43 @@ changing the template and the body of the component. When you're done, it should look like this: - - - You added two properties to the formerly empty component: `title` and `myHero`. The template displays the two component properties using double curly brace interpolation: - - -
- - The template is a multi-line string within ECMAScript 2015 backticks (\`). The backtick (\`)—which is *not* the same character as a single quote (`'`)—allows you to compose a string over several lines, which makes the HTML more readable. -
- - Angular automatically pulls the value of the `title` and `myHero` properties from the component and inserts those values into the browser. Angular updates the display when these properties change. -
- - More precisely, the redisplay occurs after some kind of asynchronous event related to the view, such as a keystroke, a timer completion, or a response to an HTTP request. -
- - Notice that you don't call **new** to create an instance of the `AppComponent` class. Angular is creating an instance for you. How? The CSS `selector` in the `@Component` decorator specifies an element named ``. That element is a placeholder in the body of your `index.html` file: - - - When you bootstrap with the `AppComponent` class (in main.ts), Angular looks for a `` in the `index.html`, finds it, instantiates an instance of `AppComponent`, and renders it inside the `` tag. @@ -109,45 +92,44 @@ Now run the app. It should display the title and hero name: The next few sections review some of the coding choices in the app. -## Template inline or template file? +## Choosing the template source +The `@Component` metadata tells Angular where to find the component's template. You can store your component's template in one of two places. -You can define it *inline* using the `template` property, or you can define -the template in a separate HTML file and link to it in -the component metadata using the `@Component` decorator's `templateUrl` property. -The choice between inline and separate HTML is a matter of taste, -circumstances, and organization policy. -Here the app uses inline HTML because the template is small and the demo -is simpler without the additional HTML file. +* You can define the template *inline* using the `template` property of the `@Component` decorator. An inline template is useful for a small demo or test. +* Alternatively, you can define the template in a separate HTML file and link to that file in the `templateUrl` property of the `@Component` decorator. This configuration is typical for anything more complex than a small test or demo, and is the default when you generate a new component. In either style, the template data bindings have the same access to the component's properties. +Here the app uses inline HTML because the template is small and the demo is simpler without the additional HTML file.
- By default, the Angular CLI command [`ng generate component`](cli/generate) generates components with a template file. You can override that with: + By default, the Angular CLI command [`ng generate component`](cli/generate) generates components with a template file. + You can override that by adding the "-t" (short for `inlineTemplate=true`) option: - ng generate component hero -it + ng generate component hero -t
-## Constructor or variable initialization? - -Although this example uses variable assignment to initialize the components, you could instead declare and initialize the properties using a constructor: +## Initialization +The following example uses variable assignment to initialize the components. + You could instead declare and initialize the properties using a constructor. + This app uses more terse "variable assignment" style simply for brevity. -This app uses more terse "variable assignment" style simply for brevity. - {@a ngFor} -## Showing an array property with ***ngFor** +## Add logic to loop through data + +The `*ngFor` directive (predefined by Angular) lets you loop through data. The following example uses the directive to show all of the values in an array property. To display a list of heroes, begin by adding an array of hero names to the component and redefine `myHero` to be the first name in the array. @@ -155,15 +137,12 @@ To display a list of heroes, begin by adding an array of hero names to the compo - -Now use the Angular `ngFor` directive in the template to display -each item in the `heroes` list. +Now use the Angular `ngFor` directive in the template to display each item in the `heroes` list. - This UI uses the HTML unordered list with `
    ` and `
  • ` tags. The `*ngFor` in the `
  • ` element is the Angular "repeater" directive. It marks that `
  • ` element (and its children) as the "repeater template": @@ -171,20 +150,13 @@ It marks that `
  • ` element (and its children) as the "repeater template": - -
    - - Don't forget the leading asterisk (\*) in `*ngFor`. It is an essential part of the syntax. For more information, see the [Template Syntax](guide/template-syntax#ngFor) page. -
    - - Notice the `hero` in the `ngFor` double-quoted instruction; it is an example of a template input variable. Read more about template input variables in the [microsyntax](guide/template-syntax#microsyntax) section of @@ -194,18 +166,13 @@ Angular duplicates the `
  • ` for each item in the list, setting the `hero` vari to the item (the hero) in the current iteration. Angular uses that variable as the context for the interpolation in the double curly braces. -
    - - In this case, `ngFor` is displaying an array, but `ngFor` can repeat items for any [iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols) object.
    - - Now the heroes appear in an unordered list.
    @@ -228,13 +195,11 @@ of hero names into an array of `Hero` objects. For that you'll need a `Hero` cla ng generate class hero -With the following code: +This command creates the following code. - - You've defined a class with a constructor and two properties: `id` and `name`. It might not look like the class has properties, but it does. @@ -245,8 +210,6 @@ Consider the first parameter: - - That brief syntax does a lot: * Declares a constructor parameter and its type. @@ -254,7 +217,6 @@ That brief syntax does a lot: * Initializes that property with the corresponding argument when creating an instance of the class. - ### Using the Hero class After importing the `Hero` class, the `AppComponent.heroes` property can return a _typed_ array @@ -273,7 +235,6 @@ Fix that to display only the hero's `name` property. - The display looks the same, but the code is clearer. {@a ngIf} @@ -291,46 +252,35 @@ To see it in action, add the following paragraph at the bottom of the template: -
    - - Don't forget the leading asterisk (\*) in `*ngIf`. It is an essential part of the syntax. Read more about `ngIf` and `*` in the [ngIf section](guide/template-syntax#ngIf) of the [Template Syntax](guide/template-syntax) page. -
    - The template expression inside the double quotes, `*ngIf="heroes.length > 3"`, looks and behaves much like TypeScript. When the component's list of heroes has more than three items, Angular adds the paragraph -to the DOM and the message appears. If there are three or fewer items, Angular omits the -paragraph, so no message appears. For more information, -see the [template expressions](guide/template-syntax#template-expressions) section of the -[Template Syntax](guide/template-syntax) page. +to the DOM and the message appears. +If there are three or fewer items, Angular omits the paragraph, so no message appears. + +For more information, see [template expressions](guide/template-syntax#template-expressions).
    - - Angular isn't showing and hiding the message. It is adding and removing the paragraph element from the DOM. That improves performance, especially in larger projects when conditionally including or excluding big chunks of HTML with many data bindings. -
    - - Try it out. Because the array has four items, the message should appear. Go back into app.component.ts and delete or comment out one of the elements from the heroes array. The browser should refresh automatically and the message should disappear. - ## Summary Now you know how to use: @@ -341,7 +291,6 @@ Now you know how to use: Here's the final code: -