Assigning a piped async result to a variable in an Angular view

If you have an Observable<x> in your component you might find yourself doing something like this {{ ( source$ | async)?.property1 }}{{ ( source$ | async)?.property2 }} This will subscribe to the source$ observable more than once. A commonly used technique to avoid this is to assign the result of the async into a view …
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Implementing a really simple Elvis Operator in TypeScript

Here is a simple routine that implements what is known as the Elvis Operator in TypeScript. In C# you can write code like thisNullable<int> age = person?.BestFriend?.Mother?.CurrentHusband?.Age); If any of the values along the way it will return a null rather than throwing a NullReferenceException. Using the class in my previous blog Get a Lambda expression …
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A type safe way of creating Angular ReactiveForms and FormGroups

If, like myself, you prefer as many of your coding mistakes to be identified at compile time as possible then you might like the following example. The FormBuilder in Angular expects us to identify our FormControls with a string name. If ever the API of your server changes then of course the names of those …
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Failed to execute ‘send’ on ‘XMLHttpRequest’: Failed to load ng:///DynamicTestModule – Solved (Angular testing)

If when you run your tests you see an error similar to this Failed to execute ‘send’ on ‘XMLHttpRequest’: Failed to load ‘ng:///DynamicTestModule/xxxxxxComponent_Host.ngfactory.js It means something in your component is throwing an exception and the test framework is returning a wrapped exception. To see the actual exception run ng test with -sm=false as a parameter …
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Angular – How to create a data aware custom component

Introduction This blog will demonstrate how to create an Angular component that you are able to add [ngModel] [formControl] and [formControlName] attributes to your custom component, and have your component correct implement the features required to work with Angular forms. Setting up the ngModule First add FormsModule and ReactiveFormsModule to your main NgModule’s import declaration …
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TypeScript – A polyfill to extend the Object class to add a values property to complement the keys property

I expect you’ve used Object.keys at some point. Here is how to extend the Object class to add a values property. This kind of thing is useful when you have a lookup of keys where all of the values are the same type, such as the following object you’d expect to see in a Redux …
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TypeScript – Get a Lambda expression as a string

One of the things I really like about C# is the ability to convert a lambda into a string. It’s useful for doing all kinds of things, especially when you are calling a 3rd party library’s method that expects a string identifying a member of an object. I saw this was lacking in TypeScript, which …
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Angular – How to create composite controls that work with formGroup/formGroupName and ReactiveForms

This blog post will show you how to create composite controls in AngularX that allow you to reuse them across your application using the formGroupName directive to data-bind them. We’ll start off with a very basic component that uses a reactive form to edit a person and their address. Editing a person’s name and address …
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Redux sub-reducer pattern for complex / nested data structures

I love the idea of the Redux pattern, the way all reducers are pure and predictable. I love the way they are effectively listeners that act on event notifications received from a central dispatcher, and I really like the way the whole approach simplifies the application and makes code in my Angular app’s components only …
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