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docs(guide): copyedit displaying-data 

Also fix a few intros while I'm in _data.json.

closes #659
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Kathy Walrath 2016-01-06 10:06:01 -08:00
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16
public/docs/ts/latest/guide/_data.json
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@ -15,12 +15,12 @@
"displaying-data": {
"title": "Displaying Data",
"intro": "In Angular, we display data by binding component properties to elements in HTML templates using interpolation and other forms of Property Binding."
"intro": "Interpolation and other forms of property binding help us show app data in the UI."
},
"user-input": {
"title": "User Input",
"intro": "User input triggers DOM events. We listen to those events with EventBindings that funnel updated values back into our components and models."
"intro": "User input triggers DOM events. We listen to those events with event bindings that funnel updated values back into our components and models."
},
"forms": {
@ -35,24 +35,24 @@
"template-syntax": {
"title": "Template Syntax",
"intro": "How to write templates that display data and consume user events with the help of data binding."
"intro": "Learn how to write templates that display data and consume user events with the help of data binding."
},
"pipes": {
"title": "Pipes",
"intro": "Pipes transform displayed values within a template"
"intro": "Pipes transform displayed values within a template."
},
"router": {
"title": "Routing & Navigation",
"intro": "Discover the basics of screen navigation with the Angular 2 router"
"intro": "Discover the basics of screen navigation with the Angular 2 router."
},
"lifecycle-hooks": {
"title": "Lifecycle Hooks",
"intro": "Angular calls lifecycle hook methods on our directives and components as it creates, changes, and destroys them."
"intro": "Angular calls lifecycle hook methods on directives and components as it creates, changes, and destroys them."
},
"attribute-directives": {
"title": "Attribute Directives",
"intro": "Attribute directives attach behavior to elements."

111
public/docs/ts/latest/guide/displaying-data.jade
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@ -3,22 +3,21 @@ include ../../../../_includes/_util-fns
<!-- http://plnkr.co/edit/x9JYbC -->
:marked
## Displaying Component Properties
We typically display data in Angular by binding controls in an HTML template
to properties of an Angular Component.
to properties of an Angular component.
In this chapter, we'll create a component with a list of heroes. Each hero has a name.
We'll display the list of hero names and
conditionally show a selected hero in a detail area below the list.
[Live Example](/resources/live-examples/displaying-data/ts/plnkr.html)
Our final UI looks like this:
The final UI looks like this:
figure.image-display
img(src="/resources/images/devguide/displaying-data/final.png" alt="Final UI")
:marked
[Run the live example](/resources/live-examples/displaying-data/ts/plnkr.html)
<a id="interpolation"></a>
.l-main-section
:marked
@ -39,25 +38,25 @@ figure.image-display
:marked
We added two properties to the formerly empty component: `title` and `myHero`.
Our revised template displays the two component properties using the double curly brace
Our revised template displays the two component properties using double curly brace
interpolation:
+makeExample('displaying-data/ts/app/app.component.1.ts', 'template')(format=".")
.l-sub-section
:marked
The template is a multi-line string within ECMAScript 2015 back-tics (\`).
The back-tick (\`) is not the same character as a single quote (').
It has many nice features. The feature we're exploiting is
the ability to compose the string over several lines which
makes for much more readable HTML.
The template is a multi-line string within ECMAScript 2015 backticks (\`).
The backtick (\`) &mdash; which is *not* the same character as a single
quote (') &mdash; has many nice features. The feature we're exploiting here
is the ability to compose the string over several lines, which makes for
much more readable HTML.
:marked
Angular automatically pulls the value of the `title` and `myHero` properties from the component and
inserts those values into the browser. Angular will update the display
inserts those values into the browser. Angular updates the display
when these properties change.
.l-sub-section
:marked
More precisely, the re-display occurs after some kind of asynchronous event related to
More precisely, the redisplay occurs after some kind of asynchronous event related to
the view such as a keystroke, a timer completion, or an async `XHR` response.
We don't have those in this sample.
But then the properties aren't changing on their own either. For the moment we must operate on faith.
@ -88,12 +87,14 @@ figure.image-display
## Template inline or template file?
We can store our component's template in one of two places.
We can define it "inline" using the template property as we do here.
We can define it *inline* using the `template` property, as we do here.
Or we can define the template in a separate HTML file and link to it in
the component metadata using the `@Component` decorator's `templateUrl` property.
We're using the *inline* style because the template is small and it makes for clearer demonstration.
The choice between them is a matter of taste, circumstances, and organization policy.
The choice between inline and separate HTML is a matter of taste,
circumstances, and organization policy.
Here we're using inline HTML because the template is small, and the demo
is simpler without the HTML file.
In either style, the template data bindings have the same access to the component's properties.
@ -106,7 +107,7 @@ figure.image-display
+makeExample('displaying-data/ts/app/app-ctor.component.ts', 'app-ctor')(format=".")
:marked
That's fine too. The choice between them is a matter of taste and organization policy.
That's fine too. The choice is a matter of taste and organization policy.
We'll adopt the more terse "variable assignment" style in this chapter simply because
there will be less code to read.
@ -116,11 +117,11 @@ figure.image-display
## Showing an array property with NgFor
We want to display a list of heroes. We begin by adding a mock heroes name array to the component,
just above `myHero` and redefine `myHero` to be the first name in the array.
just above `myHero`, and redefine `myHero` to be the first name in the array.
+makeExample('displaying-data/ts/app/app.component.2.ts', 'mock-heroes', 'app/app.component.ts (class)')(format=".")
:marked
Now we use the Angular `NgFor` "repeater" Directive in the template to display
Now we use the Angular `NgFor` "repeater" directive in the template to display
each item in the `heroes` list.
+makeExample('displaying-data/ts/app/app.component.2.ts', 'template','app/app.component.ts (template)')(format=".")
@ -132,19 +133,19 @@ figure.image-display
:marked
We added a somewhat mysterious `*ngFor` to the `<li>` element.
That's the Angular "repeater" directive.
It's presence on the `<li>` tag marks that `<li>` element (and its children) as the "repeater template".
Its presence on the `<li>` tag marks that `<li>` element (and its children) as the "repeater template".
.alert.is-important
:marked
Don't forget the leading asterisk (\*) in front of `*ngFor`. It is an essential part of the syntax.
Don't forget the leading asterisk (\*) in `*ngFor`. It is an essential part of the syntax.
Learn more about this and `NgFor` in the [Template Syntax](./template-syntax.html#ngFor) chapter.
:marked
Notice the `#hero` in the `NgFor` double-quoted instruction.
The `#hero` is a "[template local variable](./template-syntax.html#local-vars")" *declaration*.
The (#) prefix declares a local variable name named `hero`.
The `#hero` is a [local template variable](./template-syntax.html#local-vars) declaration.
The `#` prefix declares a local variable name named `hero`.
Angular will duplicate the `<li>` for each item in the list, setting the `hero` variable
Angular duplicates the `<li>` for each item in the list, setting the `hero` variable
to the item (the hero) in the current iteration. Angular uses that variable as the
context for the interpolation in the double curly braces.
@ -168,10 +169,10 @@ figure.image-display
That's fine for a demo but certainly isn't a best practice. It's not even a good practice.
Although we won't do anything about that in this chapter, we'll make a mental note to fix this down the road.
At the moment, we're binding to an array of strings. We do that occasionally in real applications but
most of the time we're displaying objects, potentially instances of classes.
At the moment, we're binding to an array of strings. We do that occasionally in real applications, but
most of the time we're displaying objects &mdash; potentially instances of classes.
Let's turn our array of hero names into an array of `Hero` objects. For that we'll need a `Hero' class.
Let's turn our array of hero names into an array of `Hero` objects. For that we'll need a `Hero` class.
Create a new file in the `app/` folder called `hero.ts` with the following short bit of code.
+makeExample('displaying-data/ts/app/hero.ts', null, 'app/hero.ts')(format = ".")
@ -179,56 +180,56 @@ figure.image-display
:marked
We've defined a class with a constructor and two properties: `id` and `name`.
If we are new to TypeScript, it may not look like we have properties. But we do. We're taking
advantage of a TypeScript short-cut in our declaration of the constructor parameters.
It might not look like we have properties, but we do. We're taking
advantage of a TypeScript shortcut in our declaration of the constructor parameters.
Consider the first parameter:
+makeExample('displaying-data/ts/app/hero.ts', 'id-parameter')
:marked
That brief syntax simultaneously
That brief syntax does a lot:
* declares a constructor parameter and its type
* declare a public property of the same name
* initializes that property with the corresponding argument when we "new" an instance of the class.
* declares a public property of the same name
* initializes that property with the corresponding argument when we "new" an instance of the class
.l-main-section
:marked
## Use the Hero class
Let's redefine the heroes property in our component to return an array of these Heroes
## Using the Hero class
Let's redefine the `heroes` property in our component to return an array of these Hero objects
and also set the `myHero` property with the first of these mock heroes.
+makeExample('displaying-data/ts/app/app.component.3.ts', 'heroes', 'app.component.ts (excerpt)')(format=".")
:marked
We'll have to update the template.
At the moment it displays the entire hero object which used to be a string value.
Let's fix that so we interpolate the `hero.name` property
At the moment it displays the entire `hero` object, which used to be a string value.
Let's fix that so we interpolate the `hero.name` property.
+makeExample('displaying-data/ts/app/app.component.3.ts', 'template','app.component.ts (template)')(format=".")
:marked
Our display looks the same but we know how much better it is under the hood.
Our display looks the same, but now we know much better what a hero really is.
<a id="ngIf"></a>
.l-main-section
:marked
## Conditional display with NgIf
Sometimes the app should display a view or a portion of a view only under prescribed circumstances.
Sometimes the app should display a view or a portion of a view only under specific circumstances.
In our example, we'd like to display a message if we have a large number of heroes ... say more than 3.
In our example, we'd like to display a message if we have a large number of heroes &mdash; say, more than 3.
The Angular `NgIf` directive will insert or remove an element based on a truthy/falsey condition.
The Angular `NgIf` directive inserts or removes an element based on a truthy/falsey condition.
We can see it in action by adding the following paragraph at the bottom of the template:
+makeExample('displaying-data/ts/app/app.component.ts', 'message')
.alert.is-important
:marked
Don't forget the leading asterisk (\*) in front of `*ngIf`. It is an essential part of the syntax.
Don't forget the leading asterisk (\*) in `*ngIf`. It is an essential part of the syntax.
Learn more about this and `NgIf` in the [Template Syntax](./template-syntax.html#ngIf) chapter.
:marked
The [template expression](./template-syntax.html#template-expressions) inside the double quotes
looks much like JavaScript and it is much like JavaScript.
looks much like JavaScript and it _is_ much like JavaScript.
When the component's list of heroes has more than 3 items, Angular adds the paragraph to the DOM and the message appears.
If there were 3 or fewer items, Angular omits the paragraph and there is no message.
If there are 3 or fewer items, Angular omits the paragraph, so no message appears.
.alert.is-helpful
:marked
@ -237,31 +238,23 @@ figure.image-display
we were conditionally including or excluding a big chunk of HTML with many data bindings.
:marked
Try it out. We have four items in the array so the message should appear.
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 hero array.
The browser should refresh automatically and the message should disappear.
Play with it.
.l-main-section
:marked
## Summary
Now we know how to
- use **interpolation** with the double curly braces to display a component property,
- use **`NgFor`** to display a list of items,
- use a TypeScript class to shape the model data for our component and display properties of that model,
- use **`NgIf`** to conditionally display a chunk of HTML based on a boolean expression.
Now we know how to use:
- **interpolation** with double curly braces to display a component property
- **`NgFor`** to display a list of items
- a TypeScript class to shape the **model data** for our component and display properties of that model
- **`NgIf`** to conditionally display a chunk of HTML based on a boolean expression
Our final code:
Here's our final code:
+makeTabs(`displaying-data/ts/app/app.component.ts,
displaying-data/ts/app/hero.ts,
displaying-data/ts/app/boot.ts`,
'final,,',
'app/app.component.ts, app/hero.ts, boot.ts')
.l-main-section
:marked
## Next Steps
In addition to displaying data, most applications need to respond to user input.
Learn about that in the [User Input](./user-input.html) chapter.