CODEWITHSUNDEEP
kotlin
poocharali
poocharali

Reputation: 11

Kotlin Incorrect null check warning

class A
{
    val b:B
    val at:String
    init
    {
        b=B(this)
        at="A's text"
    }
}

class B(a:A)
{
    val bt:String
    init
    {
        bt= if(a.at!=null) a.at.replaceFirst("A's","B's") else "else's text"
    }

}

This code will generate a warning

Condition 'a.at!=null' is always 'true'

but actually the condition 'a.at!=null' is always false.

Upvotes: 0

Views: 1000

Answers (2)

Geno Chen
Geno Chen

Reputation: 5214

This is already reported 3 years ago, as KT-10455, "Kotlin allows use of class members before initialization, leading to runtime exceptions, including NPEs on non-null types".

For temporarily fix, you can just swap the two lines in init in class A, make sure A.at is defined before used.

class A
{
    val b:B
    val at:String
    init
    {
        at="A's text"
        b=B(this)
    }
}

Upvotes: 2

Sergio
Sergio

Reputation: 30625

First you need to initialize variable at and then b:

class A
{
    val b:B
    val at:String
    init
    {
        at="A's text"
        b=B(this)

    }
}

Upvotes: 0

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