Contents
What are the types of injector hierarchies?
There are two injector hierarchies in Angular:
- ModuleInjector hierarchy—configure a ModuleInjector in this hierarchy using an @NgModule() or @Injectable() annotation.
- ElementInjector hierarchy—created implicitly at each DOM element.
What is Property injection?
Property injection is a type of dependency injection where dependencies are provided through properties. So, we need to set an object of a class that implements ICar to the Car property using Unity container. Property injection in Unity container can be implemented in two ways: Using the [Dependency] attribute.
What is used for Injection?
An injection (often and usually referred to as a “shot” in US English, a “jab” in UK English, or a “jag” in Scottish English and Scots) is the act of administering a liquid, especially a drug, into a person’s body using a needle (usually a hypodermic needle) and a syringe.
What is root injector in Angular?
We call this root Injector. This Injector becomes the root of the ElementInjector tree. The Root Component contains all other components. Angular App will create child components under the Root Component. All these child component can have their own child components creating a tree of components.
How do you inject a property?
In property injection, we need to pass object of the dependent class through a public property of the client class. Let’s use the below example for the implementation of the Property Injection or even it is called Setter Injection as value or dependency getting set in property.
How is property injection used in dependency injection?
Property Injection: In property injection (aka Setter Injection), injector supplies dependency through a public property of the client class. Method Injection: In this type of injection, client class implements an interface which declares method(s) to supply dependency and the injector uses this interface to supply dependency to the client class.
When to use property injection vs constructor injection?
If the class itself has a strong dependency upon the interface/object that you inject it with, you should use constructor injection as the class is pretty much useless without the dependency, i.e. it makes no sense to instantiate it without it. A constructor therefore enforces the dependency requirement.
How is dependency injection used to implement IOC?
Dependency Injection (DI) is a design pattern used to implement IoC. It allows the creation of dependent objects outside of a class and provides those objects to a class through different ways.
How is dependency injection used in the di pattern?
The Dependency injection pattern solves this problem by injecting dependent objects via a constructor, a property, or an interface. The following figure illustrates the DI pattern implementation for the above example.