CODEWITHSUNDEEP
androidkotlindagger-2dagger
capt.swag
capt.swag

Reputation: 10661

What's the difference between Kotlin object and class in the context of a dagger module

I was going through one of my colleagues codebase. And I found this piece of code.

@Module
object SampleAppModule {
    @Provides
    @JvmStatic
    @AppScope
    fun provideAppDependency(context: Context): AppDependency = SampleAppDependency(context)
}

And this got me thinking, how's this different from this

@Module
class SampleAppModule {
    @Provides
    @AppScope
    fun provideAppDependency(context: Context): AppDependency = SampleAppDependency(context)
}

I've seen the use of object in dagger modules recently, but I myself never used it because I didn't understand what it does. Would love to get some insights.

p.s. I tried changing the object to class, and it worked. Now I really don't know if there is any difference.

Upvotes: 2

Views: 1106

Answers (1)

Saurabh Thorat
Saurabh Thorat

Reputation: 20734

Using object to declare your Dagger modules would create only a single instance of it.

If your modules with @Provides are declared as class instead of object, then an additional object is generated on building the component. So using object, you get better performance.

Another way to do this would be using companion object. But that is not recommended:

Beyond that, don't use companion object for modules. Use object. In that case the instance will be unused and its initialization code will be removed by R8 and the methods will be truly static and can also be inlined just like Java.

Upvotes: 4

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