Swift: What does this error: 'private(set)' modifier cannot be applied to read-only properties mean?

问题

I am bit confused if we can create computed property which is read-only Somethig like:

extension ToMyClass {
    private(set) var isEmpty: Bool {
        return head == nil
    }
} 

While trying to create I got following error:

 error: 'private(set)' modifier cannot be applied to read-only properties

回答1:

You are trying to set a modfier for a computed property, which is always read-only

The code below was taken from: The Swift Programming Language (Swift 4)

struct TrackedString {
    private(set) var numberOfEdits = 0
    var value: String = "" {
        didSet {
            numberOfEdits += 1
        }
    }
}

It should be a stored property

来源：https://stackoverflow.com/questions/45660160/swift-what-does-this-error-privateset-modifier-cannot-be-applied-to-read-o