Kotlin: Funtional Type mismatch

3
votes

I'm getting below error while compiling:

Type mismatch: inferred type is (String, Boolean) -> Any but ((String, Boolean) -> Unit)? was expected

My Type Declaration is

private val ConsisFilter_Click = { filterText: String, isStrictSearch: Boolean ->

    try {
        //My Codes
    }
    catch (e: Exception) {
        try {
            alert{}.show()
        }catch (ignored: Exception) {}
    }
}



var ConsisFilterClickEvent:((filterText: String, isStrictSearch: Boolean) -> Unit)? = null

assigninkg like this

inputDialog!!.ConsisFilterClickEvent = ConsisFilter_Click

I'm following same pattern elsewhere but not getting any error. Only this particular piece is giving problem. Am I doing something wrong. Please help me.

NOTE: If I put all codes of ConsisFilter_Click (code of try catch block) into a separate function and simply call that function from ConsisFilter_Click then every this works well

Thanks

2
androidkotlin

2 Answers

5
votes

When using a lambda in Kotlin, if the inferred return type is not Unit, the last expression in it is returned. In your case, this is the try-catch statement, which also works as an expression in Kotlin.

If you want to force your lambda's return type to be Unit, you can either write down its type explicitly as stated in the other answer, or you can directly assign it to ConsisFilterClickEvent instead of storing it in another variable first - in both of these cases, the compiler will figure out that you don't want to return your last expression, and just want to use try-catch as a statement.

Another thing you can do is to explicitly return the Unit object at the end of your lambda:

private val ConsisFilter_Click = { filterText: String, isStrictSearch: Boolean ->
    try {
        ...
    }
    catch (e: Exception) {
        ...
    }
    Unit
}
3
votes

you can't assign ConsisFilter_Click to the variable ConsisFilterClickEvent since its implicit type is (String, Boolean) -> Any rather than (String, Boolean) -> Unit. due to the return type of the catch-block is Unit but the return type of the last statement of the try-block is not Unit , that will makes the lambda's return type to Any if you don't using an explicit type variable.

you must define the type of the variable ConsisFilter_Click explicitly as below:

val ConsisFilter_Click: (filterText: String, isStrictSearch: Boolean) -> Unit  = {
    filterText: String, isStrictSearch: Boolean ->

    try {
        //My Codes
    }
    catch (e: Exception) {
        try {
            alert{}.show()
        }catch (ignored: Exception) {}
    }
}