Entries for month: June 2016

Learning Angular 2: Tour of Heroes Tutorial, Lesson 5

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Lesson 5 of the Tour of Heroes tutorial introduces services.


Learning Angular 2: Tour of Heroes Tutorial, Lesson 4

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This lesson starts off with creating a new component and a separate Hero class file which is then imported into both of the current components:

import { Hero } from './hero';

Worth noting that './' is relative path syntax that indicates that the file we're importing from lives in the same directory as the current file.  


Learning Angular 2: Tour of Heroes Tutorial, Lesson 3

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Building on the lesson 2 coding exercises in the Tour of Heroes tutorial, the next lesson involves displaying a list of Hero objects.


Learning Angular 2: Tour of Heroes Tutorial, Lesson 2

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Now that I've gone through the official Angular 2 quick start tutorial, it's time to start the longer "Tour of Heroes" tutorial, starting with lesson 2 (lesson 1 is just an overview of what will be covered in the entire tutorial).


Learning Angular 2: The Official Quick Start guide

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I'm starting my Angular 2 journey with the official quick start guide on the Angular 2 website, https://angular.io/.  I'm going to use the TypeScript version of the quick start guide, since I plan on coding Angular 2 with TypeScript.  

I already have Node installed on my Mac laptop via nvm (Node Version Manager), so that's taken care of.

I want to figure out any nuances involved in using IntelliJ as my IDE for coding Angular 2 (it SHOULD work similarily to how WebStorm works in the regard), so I want to create a new IntelliJ project to house the quick start files.  Did a quick search for any IntelliJ plugins that would semi-automate the setup of a new Angular 2 codebase in an IntelliJ project, but didn't find any.  Probably just as well:  I expect to start using the Angular CLI tool for that sort of thing as I get further along anyway.  So I created a new project in IntelliJ pointed to my "angular-io-quickstart" directory.  IntelliJ expects all project files to live in modules, so I created a static web module called "root" (a module choice that doesn't come with any preconfigured structure or code files) which will hold all of the project files.  I then created all of the configuration files (package.json, tsconfig.json, etc.) in that root module.

I then ran "npm install" from the angular-io-quickstart/root directory.  A "typings" folder was created along with a "node_modules" folder, and there were "typings" modules in "node_modules", so I didn't need to execute the "npm run typings install" command cited in the guide.

The guide does a good job of explaining the different pieces of the app.component.ts file, but a few extra notes:

  • The import statement is a conventional TypeScript import statement (it's not something unique to Angular 2), so further information about its syntax can be found by searching for TypeScript articles on the web.

  • Decorators are also not exclusive to Angular:  they are also used in some server-side languages as a means of adding new properties and/or functionality to an object without using extension.

When I added the main.ts file as described, IntelliJ drew a red line under the AppComponent argument for the bootstrap function in the final line.  Hovering over the argument displayed the following error "Argument AppComponent is not assignable to parameter type Type".  The error did not prevent me from running the quick start once I finished the rest of the instructions, however.

Did some research and the solution for that is to go into the IntelliJ settings  (File/Settings in Windows / IntelliJ/Preferences in OS X), open up the Language & Frameworks settings, and in the TypeScript settings check the "Enable TypeScript Compiler" and "User tsconfig.json" options.  Reference:  http://stackoverflow.com/questions/34366797/angular-2-bootstrap-function-gives-error-argument-type-appcomponent-is-not-assi

The IntelliJ TypeScript settings also include a "Track changes" option.  With that option turned on, I don't need the compiler watcher turned on as part of the "npm start" command in the quick start instructions:  I can simply use "npm run lite" to get just the lightweight web server running, and IntelliJ will make sure my changes are picked up.  Using both "Track changes" and "npm start" together doesn't produce any sort of conflict or error however.

In either case, whether invoking the stand-alone TypeScript compiler (tsc) via the "npm start" command or via the built-in TypeScript compiler in IntelliJ, you end up generating a ".js" and "js.map" file for each ".ts" file in the project (though when IntelliJ creates those files, you can visually collapse the generated files under the TypeScript file that generated them).  I imagine that any build process that gatheres the code needed to deploy a project to production would exclude the ".ts" files (not sure whether the ".map" files would need to live on production as well).

The index.html file is pretty straightforward with the exception of the System.import statement.  If I understand things correctly, in the systemjs.config.js file:
  • The 'app' entry in the "map" object literal tells SystemJS what directory contains the 'app' modules (in this case a directory of the same name).

  • The 'app' entry in the "packages" object literal tells SystemJS that when System.import() is used with the argument 'app' (with no filename specified), it should execute the 'main.js' file...which SystemJS knows from the "map" lives in the "app" directory.

A brief consultation of the configuration API for SystemJS seems to confirm all that.

Overall, the quick start guide was easy to follow and well-explained.  Then again, it IS essentially the "Hello World" example for Angular 2, so it isn't supposed to be hard.  

Next step:  starting to work through the "Tour of Heroes" tutorial.

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