What are the differences among the three Android annotation frameworks dagger, hilt and Koin?, Retrofit benefits

[]( )Dagger

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If we want to Dagger Provide an instance of a class , All we have to do is add... To the constructor [email protected]? annotation .

After adding this annotation ,Dagger? A... Will be generated for this class at build time ?Factory. Under this use case , Because its class name is ?CompositeAdapter, It generates a file called ?CompositeAdapter**_**Factory Class .

This class contains the creation of ?CompositeAdapter? Class .

As you can see, the factory class implements ?get()? And returned a new ?CompositeAdapter? example . This is actually an implementation of this kind ?Provider ? Interface . Other classes can use ?Provider? Interface to get an instance of a class .

[]( ) If we use Hilt Instead of Dagger Well ？

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In this case , It doesn't make any difference .Hilt? Is an internal use ?Dagger? The library of , The class I show you is composed of ?Dagger? Generated . If you use ?Hilt, It does generate some additional classes for us , These classes simplify ?Dagger? Use , And reduce the amount of boilerplate code we need to write . But the core remains the same .

[]( )Koin

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Koin? And ?Dagger? as well as ?Hilt? comparison , The approach to managing dependencies is completely different . To be in Koin Register dependencies in , We won't use any annotations , because Koin No code will be generated . contrary , We must provide factories for modules , These modules will be used to create instances of each class required in the project .

Koin? Add references to these factory classes to ?InstancesRegistry? Class , This class contains references to all the factories we write .

The ?map? Medium ?key? Is the full name of the class or the name provided when using named parameters . The corresponding value is the factory we write , Will be used to create an instance of the class .

To get dependencies , We need to call ?get()?( For example, in a factory class ) Or through ?activities? or ?fragments? Call in ?inject()? Delegate properties , So as to load ?get().get() Method will find the factory registered for the class of the given type , And inject it into it .

[]( ) What's the impact? ？

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Dagger Generate code to provide dependencies , and Koin No code generation , This actually has some impact .

1. Error handling

because Dagger? Is a compile time dependency injection framework , If we forget to provide some dependencies , We will know our mistakes almost immediately , Because our project will fail to build .

for example , If we forget to write to the constructor ?CompositeAdapter? Add [email protected]? annotation , And try to inject it into fragment in , The build will fail , And display the appropriate error , Tell us exactly what's wrong .

stay Koin The situation is different in , Because it doesn't generate any code . If we forget to be ?CompositeAdapter Class add factory , The application will be successfully built , But it will throw out ?RuntimeException? Once we request an instance of this class . It may happen when the application starts , So we may notice it immediately , But it may also happen later on other screens or when the user performs certain actions .

2. Impact on build time

Koin The advantage of not generating any code is ： It has a much smaller impact on our build time .Dagger? You need to use an annotation processor to scan the code and generate the appropriate classes . This may take some time , It may slow down our construction .

summary

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