Calls a function once for each immediate child of a tree.
- iOS 2.0+
- macOS 10.0+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
- Core Foundation
The tree to operate upon.
The callback function to call once for each child in
tree. The function must be able to apply to all the values in the tree.
A pointer-sized program-defined value that is passed to the applier function, but is otherwise unused by this function.
Note that the applier only operates one level deep—it does not operate on descendants further removed than the immediate children of a tree. If the tree is mutable, it is unsafe for the applied function to change the contents of the tree.