Override non-dynamic class delaration

Question

With new Xcode 8.3, I get the error:

Cannot override a non-dynamic class declaration from an extension

from the line of code:

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell

How I can avoid this warning?

see this http://stackoverflow.com/questions/41869177/cant-override-uitableviewdatasource-and-uitableviewdelegate — Anbu.Karthik, Mar 29 '17 at 08:02
You avoid the warning by not overriding in an extension – do the override in the main body of the class. Compare http://stackoverflow.com/q/38213286/2976878 — Hamish, Mar 29 '17 at 08:05

score 17 · Answer 1 · edited Jun 28 '21 at 17:13

17

Extensions can add new functionality to a type, but they cannot override existing functionality.

You have two options:

Move your method inside the Class-scope, instead of extension.
Add dynamic type to your method (where it's defined), like example.

Example:

@objc open dynamic func onLog(_ message: String) -> Void {
    print("Info: \(message)");
}

edited Jun 28 '21 at 17:13

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answered Feb 14 '18 at 09:22

jamal zare

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score 6 · Answer 2 · edited Jan 12 '21 at 16:49

which means, you can't not override like super class delegate method in extension. the way you can do is mv extension override method to subclass declare.

final class DEMO, UITableViewDataSource, UITableViewDelegate { 

    override func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
         return sectionHeader
    }

    override func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
         return 40
    }

}

Override non-dynamic class delaration

2 Answers2

Example:

Linked