Guice TypeLiterals in Kotlin

Question

I have a scenario where I have a generic interface and wish to bind multiple implementations of that interface in Guice. Normally in Java this would mean TypeLiterals, how would this be done in Kotlin?

bind(TypeLiteral<Resolver<RealObject>>(){}).to(RealResolver::class.java)

This gives a compiler error of: cannot access <init>: it is public/*package*/ in 'TypeLiteral'

There is a TypeLiteral.get() method however I cannot seem to get that to work either

hotkey · Accepted Answer · 2018-03-13 16:54:27Z

Instead of the Java anonymous class syntax (new TypeLiteral<Resolver<RealObject>>(){}), you should use the Kotlin object expression:

bind(object : TypeLiteral<Resolver<RealObject>>() { }).to(RealResolver::class.java)

You can wrap that into an inline function with a reified type parameter:

inline fun <reified T> typeLiteral() = object : TypeLiteral<T>() { }

Then use it as:

bind(typeLiteral<Resolver<RealObject>>()).to(RealResolver::class.java)

I just want to add to this that it compiles as above - however remember to add @JvmSuppressWildcards on the injection points and the declaration For example bind(object : TypeLiteral<Resolver<@JvmSuppressWildcards RealObject>>() { }).to..... Then to implement class InjectionTest @Inject constructor(resolver: Resolver<@JvmSuppressWildcards RealObject>

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