"conflicts with previous declaration" in Swift extension

Question

Created Jul ’15

Replies 2

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Hi guys.

I just finished the WWDC 2015 video "Improving Your Existing Apps with Swift" and I want to try out extending my existing classes with Swift. At around 25:16 of the WWDC video, there's this part where the speaker overrides a UITableViewDelegate method - tableView:accessoryButtonTappedForRowWithIndexPath: in his Swift file.

I tried to do the same thing to my extension, but with - tableView:heightForRowAtIndexPath:. The problem is I am getting a compiler error:

Method 'tableView(_:heightForRowAtIndexPath:)' with Objective-C selector 'tableView:heightForRowAtIndexPath:' conflicts with previous declaration with the same Objective-C selector

I did not implement this method in my Objective-C file so I don't know why it clashes. Tried it on the latest Xcode 7.0 Beta (7A152u) and Xcode 6.4. Got the same error.

Answered by allanrvj in 25984022

Thanks. I added the return type and a stub of returning 1.0, but it is still reporting the same compiler error.

Also, it's not a class but a Swift extension of an Objective-C class. As in:

import Foundation
extension TestTableViewController {

    func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return 1.0
    }
}

Doesn't compile.

Edit: I know now. Insert a "public override". Now it compiles 🙂

import Foundation
extension TestTableViewController {

    public override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return 1.0
    }
}

There is a fix-it suggestion on Xcode 7.0 which is not available in Xcode 6.4. Also, it doesn't compile on Xcode 6.4 but compiles on Xcode 7.0 Beta.

Boost

Answer 1

LCS OP

Jul ’15

It sounds like your method has a different signature than the delegate method.

Does it look like this:

class TestDelegate: NSObject, UITableViewDelegate
{
    func tableView(tableView: UITableView, heightForRowAtIndexPath: NSIndexPath) -> CGFloat
    {
       
        return 1.0
    }
}

0

Answer 2

allanrvj OP