199 lines
7.8 KiB
Plaintext
199 lines
7.8 KiB
Plaintext
include ../../../../_includes/_util-fns
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:marked
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# Once Upon a Time
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Every story starts somewhere. Our story starts where the [QuickStart](../quickstart.html) ends.
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[Run the live example for part 1](/resources/live-examples/toh-1/ts/plnkr.html)
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Follow the "QuickStart" steps. They provide the prerequisites, the folder structure,
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and the core files for our Tour of Heroes.
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Copy the "QuickStart" code to a new folder and rename the folder `angular2-tour-of-heroes`.
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We should have the following structure:
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.filetree
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.file angular2-tour-of-heroes
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.children
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.file app
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.children
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.file app.component.ts
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.file main.ts
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.file node_modules ...
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.file typings ...
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.file index.html
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.file package.json
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.file tsconfig.json
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.file typings.json
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:marked
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## Keep the app transpiling and running
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We want to start the TypeScript compiler, have it watch for changes, and start our server. We'll do this by typing
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code-example(format="" language="bash").
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npm start
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:marked
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This command runs the compiler in watch mode, starts the server, launches the app in a browser,
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and keeps the app running while we continue to build the Tour of Heroes.
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.l-main-section
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:marked
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## Show our Hero
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We want to display Hero data in our app
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Let's add two properties to our `AppComponent`, a `title` property for the application name and a `hero` property
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for a hero named "Windstorm".
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'app-component-1', 'app.component.ts (AppComponent class)')(format=".")
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:marked
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Now we update the template in the `@Component` decoration with data bindings to these new properties.
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'show-hero')
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:marked
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The browser should refresh and display our title and hero.
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The double curly braces tell our app to read the `title` and `hero` properties from the component and render them.
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This is the "interpolation" form of one-way data binding.
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.l-sub-section
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:marked
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Learn more about interpolation in the [Displaying Data chapter](../guide/displaying-data.html).
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:marked
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### Hero object
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At the moment, our hero is just a name. Our hero needs more properties.
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Let's convert the `hero` from a literal string to an interface.
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Create a `Hero` interface with `id` and `name` properties.
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Keep this near the top of the `app.component.ts` file for now.
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+makeExample('toh-1/ts/app/app.component.ts', 'hero-interface-1', 'app.component.ts (Hero interface)')(format=".")
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.l-sub-section
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:marked
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#### Interface or Class?
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Why a `Hero` interface and not a `Hero` class?
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We want a strongly typed `Hero`. We get strong typing with either option.
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Our choice depends on how we intend to use the `Hero`.
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If we need a `Hero` that goes beyond simple properties, a `Hero` with logic and behavior,
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we must define a class.
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If we only need type checking, the interface is sufficient and lighter weight.
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Lighter weight? Transpiling a class to JavaScript produces code.
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Transpiling an interface produces — nothing.
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If the class does nothing (and there is nothing for a `Hero` class to do right now),
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we prefer an interface.
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:marked
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Now that we have a `Hero` interface, let’s refactor our component’s `hero` property to be of type `Hero`.
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Then initialize it with an id of `1` and the name, "Windstorm".
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'hero-property-1', 'app.component.ts (Hero property)')(format=".")
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:marked
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Because we changed the hero from a string to an object,
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we update the binding in the template to refer to the hero’s `name` property.
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'show-hero-2')
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:marked
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The browser refreshes and continues to display our hero’s name.
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### Adding more HTML
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Displaying a name is good, but we want to see all of our hero’s properties.
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We’ll add a `<div>` for our hero’s `id` property and another `<div>` for our hero’s `name`.
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'show-hero-properties')
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:marked
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Uh oh, our template string is getting long. We better take care of that to avoid the risk of making a typo in the template.
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### Multi-line template strings
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We could make a more readable template with string concatenation
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but that gets ugly fast, it is harder to read, and
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it is easy to make a spelling error. Instead,
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let’s take advantage of the template strings feature
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in ES2015 and TypeScript to maintain our sanity.
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Change the quotes around the template to back-ticks and
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put the `<h1>`, `<h2>` and `<div>` elements on their own lines.
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'multi-line-strings', 'app.component.ts (AppComponent\'s template)')
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.callout.is-important
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header A back-tick is not a single quote
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:marked
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**Be careful!** A back-tick (`) looks a lot like a single quote (').
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It's actually a completely different character.
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Back-ticks can do more than demarcate a string.
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Here we use them in a limited way to spread the template over multiple lines.
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Everything between the back-ticks at the beginning and end of the template
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is part of a single template string.
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.l-main-section
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:marked
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## Editing Our Hero
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We want to be able to edit the hero name in a textbox.
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Refactor the hero name `<label>` with `<label>` and `<input>` elements as shown below:
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+makeExample('toh-1/ts-snippets/app.component.snippets.pt1.ts', 'editing-Hero', 'app.component.ts (input element)')
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:marked
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We see in the browser that the hero’s name does appear in the `<input>` textbox.
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But something doesn’t feel right.
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When we change the name, we notice that our change
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is not reflected in the `<h2>`. We won't get the desired behavior
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with a one-way binding to `<input>`.
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### Two-Way Binding
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We intend to display the name of the hero in the `<input>`, change it,
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and see those changes wherever we bind to the hero’s name.
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In short, we want two-way data binding.
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Let’s update the template to use the **`ngModel`** built-in directive for two-way binding.
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.l-sub-section
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:marked
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Learn more about `ngModel` in the
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[Forms](../guide/forms.html#ngModel) and
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[Template Syntax](../guide/template-syntax.html#ngModel) chapters.
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:marked
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Replace the `<input>` with the following HTML
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code-example(language="html").
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<input [(ngModel)]="hero.name" placeholder="name">
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:marked
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The browser refreshes. We see our hero again. We can edit the hero’s name and
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see the changes reflected immediately in the `<h2>`.
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.l-main-section
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:marked
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## The Road We’ve Travelled
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Let’s take stock of what we’ve built.
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* Our Tour of Heroes uses the double curly braces of interpolation (a form of one-way data binding)
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to display the application title and properties of a `Hero` object.
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* We wrote a multi-line template using ES2015’s template strings to make our template readable.
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* We can both display and change the hero’s name after adding a two-way data binding to the `<input>` element
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using the built-in `ngModel` directive.
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* The `ngModel` directive also propagates changes to every other binding of the `hero.name`.
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[Run the live example for part 1](/resources/live-examples/toh-1/ts/plnkr.html)
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Here's the complete `app.component.ts` as it stands now:
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+makeExample('toh-1/ts/app/app.component.ts', 'pt1', 'app.component.ts')
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.l-main-section
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:marked
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## The Road Ahead
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Our Tour of Heroes only displays one hero and we really want to display a list of heroes.
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We also want to allow the user to select a hero and display their details.
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We’ll learn more about how to retrieve lists, bind them to the
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template, and allow a user to select it in the
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[next tutorial chapter](./toh-pt2.html). |