FocusBinding

public struct FocusBinding

A two-way binding between a focusable element’s backing view and a FocusState-wrapped property.

Generally you should not need to interact with this type directly. However, you can use focus bindings to add focus support to custom elements.

Adding Focus Bindings

On a FocusState, call the binding(for:) method to get a binding bound to an optional value, or binding() to get a binding bound to a boolean.

To set up the 2-way binding, there are 2 steps:

1. Assign actions to the nested FocusTrigger, so that your backing view is updated when the FocusState‘s value changes.

2. Call the onFocus and onBlur callbacks when your backing view gains or loses focus, so that the value of the bound FocusState is updated.

Example

final class FocusableView: UIView {
    var focusBinding: FocusBinding? {
        didSet {
            oldValue?.trigger.focusAction = nil
            oldValue?.trigger.blurAction = nil

            guard let focusBinding = focusBinding else { return }

            focusBinding.trigger.focusAction = { [weak self] in
                self?.becomeFirstResponder()
            }
            focusBinding.trigger.blurAction = { [weak self] in
                self?.resignFirstResponder()
            }

            if isFirstResponder {
                focusBinding.onFocus()
            } else {
                focusBinding.onBlur()
            }
        }
    }

    @discardableResult
    override func becomeFirstResponder() -> Bool {
        let focused = super.becomeFirstResponder()
        if focused {
            focusBinding?.onFocus()
        }
        return focused
    }

    @discardableResult
    override func resignFirstResponder() -> Bool {
        let blurred = super.resignFirstResponder()
        if blurred {
            focusBinding?.onBlur()
        }
        return blurred
    }
}

• Tag: FocusBinding