ng-units

Angular component library for units of measurement. https://hansmaad.github.io/ng-units/

Basic concepts

There are many different ways to deal with physical units in software applications. Here is how we do it in ng-units.

At first, some basic terms we use in ng-units:

• Quantity: e.g.: Length, Mass, Temperature
• Unit: e.g.: meter, kilogram, Kelvin
• System of units: A collection of quantities and their units.

When using ng-units, you will store all your model values (and probably all your data on the backend side) based on one single consistent set of base units. ng-units uses the SI base units kg, m, s, A, K, mol, cd but you're free to define your own quantities by using any base units you like.

Your entire code should handle values based on these base units. When calculating stuff using these values, it's clear that results are also based on base units. E.g. when multiplying two length quantites, the result is stored in m². The only moment, when we start converting numbers, is to render them to the view or getting input from the view. Both is handled by the components, directive and pipes of ng-units.

Basic usage

Your app must have at least on systemOfUnits. When importing the NgUnitsModule into your app module, the systemOfUnits provider will be registered into the root injector of your app.

@NgModule({
  imports: [
    BrowserModule,
    NgUnitsModule.forRoot(),
  ], //...
})
export class AppModule { }

To initialize your system of units (adding predefined or custom quantities to it), pass a SystemOfUnitsConfig to forRoot(). Usually you'd like to implement an initializer for this config in a separate file.

export function systemOfUnitsInitializer(): SystemOfUnitsConfig {
    return {
        quantities: [area, length, time, new Quantity(/**/), /*...*/]
    }
}

@NgModule({
  imports: [
    BrowserModule,
    NgUnitsModule.forRoot(systemOfUnitsInitializer()),
  ], //...
})

If you want to import the NgUnitsModule into lazy loaded modules without creating a new system of units, use NgUnitsModule.forChild().

It's possible to provide separate systems of units on component or module level.

ngQuantity pipe

To simply render converted values, use the ngQuantity pipe. You can pass the quantity as a string, to select the quantity from the systemOfUnits or you can bind to a quantity instance in your controller. If you want to show the unit symbol, use :true.

<p>My value without label: {{value | ngQuantity:'Length'}}</p>
<p>My value with label: {{value | ngQuantity:'Length':true}}</p>
<p>My value with dynamic quantity: {{value | ngQuantity:myQuantity}}</p>

ngQuantity directive

To use a quantity with ngModel, use the ngQuantity directive. You can pass the quantity as a string, to select the quantity from the systemOfUnits or you can bind to a quantity instance in your controller.

<input name="val1" [(ngModel)]="value" ngQuantity="Length">
<input name="val2" [(ngModel)]="value" [ngQuantity]="myQuantity">

ngUnitSelect

Use the ngUnitSelect attribute component, to fill a <select> with units of a quantity.

<select ngUnitSelect="Length"></select>
<select [ngUnitSelect]="myQuantity"></select>

If you implement your own mechanism to change units, remember to broadcast this change to the system of units or use the selectUnit method, which will then broadcast the change.

// After modifiying quantity do
this.systemOfUnits.broadcast(quantity);
// OR
this.systemOfUnits.selectUnit(quantity, newUnit);