Dagger ‐ Named annotation and qualifiers

Contents
Observations
Output
Code

Observations

• The named annotations or qualifiers are used to differentiate between two different values in a single class type that is being injected using the dagger.
• One such scenario is say you have an interface and 2 different implementations of the interface, Now you create 2 modules for this interface and then add both the modules in the component you are preparing. This would result in an error since dagger doesn't understand which implementation to use.
• We can resolve this by specifying a qualifier for this purpose.

Output

OS type is Android

Code

Contents
Implementations
Qualifiers
Modules
Components
Activity

Implementations

OS.kt

interface OS {
    fun getOsType()
}

AndroidOs.kt

class AndroidOs @Inject constructor() : OS {
    override fun getOsType() {
        printLog("OS type is Android")
    }
}

AppleOs.kt

class AppleOs @Inject constructor() : OS {
    override fun getOsType() {
        PrintUtils.printLog("OS type is IOS")
    }
}

Qualifiers

Modules

Components

Activity