Kotlin Contract

Oct 18, 2019

As of Kotlin 1.3.50

  • Contract is experimental
  • Used on top-level functions only (cannot be used on class field and property)
  • Currently the Kotlin compiler does not verify contracts, so it's a programmer's responsibility to write correct and sound contracts
@UseExperimental(ExperimentalContracts::class)fun FirebaseUser?.isAuthenticated(): Boolean {    contract {        returns(true) implies (this@isAuthenticated != null)    }    return this != null}
val auth = FirebaseAuth.getInstance()val user: FirebaseUser? = auth.currentUserif (user.isAuthenticated()) {    // further checking is not required as user is guaranteed to be non null    val uid: String = user.uid    // without contract    // val uid: String? = user?.uid}

References:

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✨ By Desmond Lua

A dream boy who enjoys making apps, travelling and making youtube videos. Follow me on @d_luaz

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