file io in IOS kotlin native KMM / compose multiplatform file read write in ios

PlatformFileWriter.kt

// file io in IOS kotlin native KMM / compose multiplatform file read write in ios
//common main
expect class PlatformFileWriter() {
    fun read(filename: String): String?
    fun save(filename: String, content: String)
    fun append(filename: String, content: String)
}






//ios main
@file:OptIn(ExperimentalForeignApi::class, ExperimentalForeignApi::class)

import kotlinx.cinterop.ExperimentalForeignApi
import platform.Foundation.NSDocumentDirectory
import platform.Foundation.NSFileHandle
import platform.Foundation.NSSearchPathForDirectoriesInDomains
import platform.Foundation.NSString
import platform.Foundation.NSUTF8StringEncoding
import platform.Foundation.NSUserDomainMask
import platform.Foundation.closeFile
import platform.Foundation.dataUsingEncoding
import platform.Foundation.fileHandleForWritingAtPath
import platform.Foundation.seekToEndOfFile
import platform.Foundation.stringByAppendingPathComponent
import platform.Foundation.stringWithContentsOfFile
import platform.Foundation.writeData
import platform.Foundation.writeToFile


actual class PlatformFileWriter actual constructor() {


    actual  fun read(  filename: String) : String? {
        val documentDirectory = NSSearchPathForDirectoriesInDomains(
            NSDocumentDirectory,
            NSUserDomainMask,
            true
        )[0] as NSString

        // Append the file name to the document directory path
        val filePath = documentDirectory.stringByAppendingPathComponent(filename)

        return NSString.stringWithContentsOfFile(filePath, NSUTF8StringEncoding, null)
    }

    actual  fun save( filename : String, content : String) {


        val documentDirectory = NSSearchPathForDirectoriesInDomains(
            NSDocumentDirectory,
            NSUserDomainMask,
            true
        )[0] as NSString

        // Append the file name to the document directory path
        val filePath = documentDirectory.stringByAppendingPathComponent(filename)



        (content as NSString).writeToFile(filePath, true, NSUTF8StringEncoding, null)
    }


    actual fun append(filename: String, content: String) {
        val documentDirectory = NSSearchPathForDirectoriesInDomains(
            NSDocumentDirectory,
            NSUserDomainMask,
            true
        )[0] as NSString

        // Append the file name to the document directory path
        val filePath = documentDirectory.stringByAppendingPathComponent(filename)


        // Open the file in append mode
        val fileHandle = NSFileHandle.fileHandleForWritingAtPath(filePath) ?: run {
            // If the file doesn't exist, create it
            (content as NSString) .writeToFile(filePath, true, NSUTF8StringEncoding, null)
            return
        }

        // Move to the end of the file
        fileHandle.seekToEndOfFile()

        // Convert NSString to NSData
        val data = (content as NSString).dataUsingEncoding(NSUTF8StringEncoding)!!

        // Write content to the end of the file
        fileHandle.writeData(data)

        // Close the file handle
        fileHandle.closeFile()
    }




}







//usage
PlatformFileWriter().save("textFile.txt","Lorem ipsum")
PlatformFileWriter().read("textFile.txt",)