给NextGrowingTextView添加扩展，支持设置光标大小。
NextGrowingTextView是一个第三方库，内部有一个继承自UITextView的NextGrowingInternalTextView，这个textview外部是访问不了的。而设置textview的光标大小需要继承UITextView并重写UITextInput.caretRect(for:)方法。怎么办呢？
大概有三种办法：
1、私有化NextGrowingTextView。直接改NextGrowingInternalTextView类。这种最简单，但是以后就需要自己维护这个库了。
2、方法交换UITextView的caretRect(for:)实现。这种也比较简单，但是由于交换的是UITextView的实现，影响的范围比较大。
3、动态给NextGrowingInternalTextView添加caretRect(for:)实现。这个影响的范围只有NextGrowingInternalTextView，并且也不需要私有化NextGrowingTextView。个人觉得是最佳的解决办法了。这个方案的难点是添加自己的实现后怎么调用父类的实现。解决办法就是先获取父类的IMP，再添加自己的实现。
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| extension NextGrowingTextView {
private struct AssociatedKeys {
static var caretSize = "caretSize"
}
var caretSize: CGSize? {
get {
return objc_getAssociatedObject(self, &AssociatedKeys.caretSize) as? CGSize
}
set {
objc_setAssociatedObject(self, &AssociatedKeys.caretSize, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
hookCaretRectMethodOnce()
}
}
private func hookCaretRectMethodOnce() {
DispatchQueue.once {
let cls: AnyClass = type(of: self.textView)
let sel: Selector = #selector(UITextInput.caretRect(for:))
guard let originalMethod = class_getInstanceMethod(cls, sel) else {return}
let originalIMP = method_getImplementation(originalMethod)
typealias Function = @convention(c) (AnyObject, Selector, Any?) -> CGRect
let function = unsafeBitCast(originalIMP, to: Function.self)
let implementBlock: @convention(block) (UITextView, UITextPosition) -> CGRect = { (textView, position) -> CGRect in
var rect = function(textView, sel, position)
guard let parentView = textView.superview as? NextGrowingTextView else {return rect}
guard let caretSize = parentView.caretSize else {return rect}
rect.origin.y -= (caretSize.height - rect.size.height)
rect.size = caretSize
return rect
}
let types = "{CGRect={CGPoint=dd}{CGSize=dd}}@:@"
class_addMethod(cls, sel, imp_implementationWithBlock(unsafeBitCast(implementBlock, to: AnyObject.self)), types)
}
}
}
|
参考
每周 Swift 社区问答：@convention
