在代码中设置“用户定义的运行时属性”

Question

This may be a silly question but I couldn't find an answer anywhere. If I want to create a UIButton in code and need to set a runtime attribute how would I do so without the interface builder and strictly in code?

Answer 1

Actually figured this out, like I said silly question.

[UIButton *loginbtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[loginbtn setValue:@"blah" forKey:@"myAttr"];

Answer 2

When you set a runtime attribute in Interface Builder, what you're actually doing is instructing the Nib loading machinery to call the corresponding setter method on that object during Nib loading. So, if you have a runtime attribute called for example "name" with a string value of "Bob", all that means is that at some point at runtime during Nib loading, the instance's -setName: method will be called with @"Bob" as the argument.

So, to do the same thing at runtime, you just set the property directly, perhaps in your view controller's -viewDidLoad method, or another appropriate place:

self.button.name = @"Bob";

Answer 3

Wanted to provide an updated answer which leverages Swift property wrappers to cleanly attribute UI elements which should be ignored.

Swift 5.1+ Property Wrapper

@propertyWrapper
public struct HeapIgnore<T> {
    public var wrappedValue: T {
        didSet {
            (wrappedValue as? NSObject)?.setValue(true, forKey: "heapIgnore")
        }
    }

    public init(wrappedValue: T) {
        self.wrappedValue = wrappedValue
    }
}

Example Usage

... // Inside ViewController
@HeapIgnore
@IBOutlet private var passwordTextField: UITextField!

I've implemented this solution and confirmed in both the Live View and Events Visualizer that Heap ignores events generated by UI elements attributed with the property wrapper.

Answer 4

You need to reference somehow the UIButton in the code (usually by creating an IBOutlet) and then you can access its properties as you would do when you create a button programmatically.

If you want to create the button programmatically for instance:

    UIButton *button = [[UIButton alloc] initWithFrame:frame];
    [button setTitle:@"Title" forState:UIControlStateNormal];