Super.method() calls overriden method in a subclass?

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Kotlin

class UpperCaseWriter(realWriter: Writer) : FilterWriter(realWriter) {

    override fun write(cbuf: CharArray, off: Int, len: Int) {
        val newBuff = CharArray(len)
        cbuf.copyInto(newBuff, destinationOffset = 0, startIndex = off, endIndex = off + len)
        newBuff.indices.forEach { n ->
            newBuff[n] = newBuff[n].uppercaseChar()
        }

        super.write(newBuff) // This should call FilterWriter's write method
    }//but it seems it calls the below write() function that takes str not chararray

    override fun write(str: String, off: Int, len: Int) {
        super.write(str.uppercase(), off, len) // but this is with different signiture?
    }
}

I am sorry for this basic question.
Is it because of delegation to realwriter(except for overriden methods ), if so why super?

What I have tried:

I thought it was overloading. But I am lost.

Posted 30-Jul-24 18:49pm

Member 13798091

Updated 30-Jul-24 23:03pm

M-Badger

v2

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Member 13798091 31-Jul-24 6:59am

The problem is that when I delete uppercase() from this
super.write(str.uppercase(), off,
len)
It will not print the text uppercased?
And when I hit ctrl and click on write from this super.write(newbuf) it takes to me the write(str, off,
len) that is overriden bellow it?

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OriginalGriff · Answer 1 · 2024-07-30T19:39:00

Solution 1

I'm not a Kotlin expert, but the method signature doesn't match: your new method requires 3 parameters (CharArry, Int, and Int) but your call provides only one.

In most languages, overloaded methods are only called when the parameters match. I'd suspect Kotlin is the same.

Posted 30-Jul-24 19:39pm

OriginalGriff

Comments

Member 13798091 31-Jul-24 7:00am

The problem is that when I delete uppercase() from this
super.write(str.uppercase(), off,
len)
It will not print the text uppercased?
And when I hit ctrl and click on write from this super.write(newbuf) it takes to me the write(str, off,
len) that is overriden bellow it?

M-Badger · Answer 2 · 2024-07-30T23:13:00

Solution 2

If I understand Kotlin method resolution then unless the superclass has a method with the signature fun write(CharArray) then Kotlin resolves the method call based on the most specific match available which in this case is your override fun write(str: String, off: Int, len: Int) method.

So as OG said, you need to make the super.write call match a method signature that is present in the superclass.

Posted 30-Jul-24 23:13pm

M-Badger

Comments

Member 13798091 31-Jul-24 7:01am

The problem is that when I delete uppercase() from this
super.write(str.uppercase(), off,
len)
It will not print the text uppercased?
And when I hit ctrl and click on write from this super.write(newbuf) it takes to me the write(str, off,
len) that is overriden bellow it?

M-Badger 1-Aug-24 4:17am

Update your question with the write method (and any overloads) from the superclass then someone might be able to help

Member 13798091 · Answer 3 · 2024-08-03T03:34:00

fun main() {
    UpperCaseWriter(FileWriter("log.txt")).use {
        it.write(
            """
            This is a test 
            another line 
            SOME UPPERCASE TEXT
        """.trimIndent())
    }
}
//I think here, it.write(str) calls from java API Writer.java:

public void write(String str) throws IOException {
    write(str, 0, str.length())}
//and this write(str, 0, str.length())
//calls my overriden fun write that is: 
    override fun write(str: String, off: Int, len: Int) {
        super.write(str.uppercase(), off, len)
    }
//as I am delegating to realwriter that it use all the methods except for the overriden ones, Am I right here?

Super.method() calls overriden method in a subclass?

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