So, in Kotlin, a normal property can’t hold a null value. If you are familiar with Java, then must have encountered withĪnd to remove this or in other words, we can say that to safely deal with this NullPointerException, the developers of Kotlin introduced Null safety. However, they are already used in the Kotlin standard library and have been available since version 1.3.60 of Kotlin.So, it seems that Kotlin contracts are here to stay.Null safety is one of the best features of Kotlin. They may change in the future or even be removed. Kotlin contracts are an experimental feature of Kotlin. So make sure that you hold your promise, especially for contracts placed in a public function. This means that if you specify that a function will return a non-null value, you can still return null, and the compiler will not complain. The compiler trusts you with the contracts. It’s important to note that even though you specify something with a contract, you can still return anything. val nullValue : String? = null onl圜ontract(nullValue) println(nullValue.length) // no problem for compiler Note fun Any?.isNotNull(): Boolean īy using this function above, you can get rid of the nullability issue which prevents the code to be compiler by the compiler. One, very basic example of a Kotlin contract is the isNotNullfunction. They allow a function to explicitly describe its behavior in a way that is understood by the compiler. Kotlin contracts are an extension of this concept that was introduced in version 1.3.60 of Kotlin.

Contracts in programming are agreements between different parts of the code.

Kotlin if not null