I’d like to implement `UITableViewDataSourceProtoc...

# ios

[jessewilson]

I’d like to implement UITableViewDataSourceProtocol in pure Kotlin (1.8.20 !), and I’m running into problems with Objective-C conflicting overloads.

My code looks like this:

private val tableViewDataSource: UITableViewDataSourceProtocol =
    object : NSObject(), UITableViewDataSourceProtocol {
      override fun numberOfSectionsInTableView(
        tableView: UITableView,
      ): NSInteger = ...

      override fun tableView(
        tableView: UITableView,
        numberOfRowsInSection: NSInteger,
      ): NSInteger = ...

      override fun tableView(
        tableView: UITableView,
        cellForRowAtIndexPath: NSIndexPath,
      ): UITableViewCell = ...
    }

Which triggers a failure in the compileCommonMainKotlinMetadata task:

> Task :redwood-treehouse-lazylayout-uiview:compileCommonMainKotlinMetadata FAILED

e: file:///Volumes/Development/redwood/redwood-treehouse-lazylayout-uiview/src/commonMain/kotlin/app/cash/redwood/treehouse/lazylayout/uiview/UIViewLazyList.kt:93:10 

Return type of 'tableView' is not a subtype of the return type of the overridden member
  'public open expect fun tableView(tableView: UITableView, canMoveRowAtIndexPath: NSIndexPath): Boolean 
defined in platform.UIKit.UITableViewDataSourceProtocol'

A similar issue has come up before here. I don’t think compiling Kotlin metadata was necessary in 2018.

Any recommendations on how to work-around or fix this? I’m currently disabling the task in Gradle and that feels bad.

tasks.configureEach { task ->
  if (task.name == "compileCommonMainKotlinMetadata") {
    task.onlyIf { false }
  }
}

[ribesg]

You can suppress these errors. I suppress them at the file level to not pollute code:

@file:Suppress(
    "PARAMETER_NAME_CHANGED_ON_OVERRIDE",
    "RETURN_TYPE_MISMATCH_ON_OVERRIDE"
)

[louiscad]

I fear suppression of errors will go away in future Kotlin versions. I'd submit an issue about that specific problem on kotl.in/issue