Swift:将对象转换为其他对象
我创建了UIView的扩展,在UIKeyboard上为UITextField/UITextView添加UIToolbar。Swift:将对象转换为其他对象
extension UIView {
public func addDoneOnKeyboardWithTarget (target : AnyObject, action : Selector) {
//Creating UIToolbar
var toolbar = UIToolbar()
//Configuring toolbar
var items = NSMutableArray()
var nilButton = IQBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.FlexibleSpace, target: nil, action: nil)
items.addObject(nilButton)
var doneButton = IQBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.Done, target: target, action: doneAction)
items.addObject(doneButton)
toolbar.items = items
//Now typecasting self to UITextField for compilation purposes because `inputAccessoryView` is readonly for UIView. it's readwrite for UITextField and UITextView both.
var textField : UITextField = self as UITextField //Runtime error for UITextView
//Setting new toolbar as inputAccessoryView
textField.inputAccessoryView = toolbar
}
}
它适用于UITextField,但是当我在UITextView上调用上述函数时,它在类型转换时崩溃。
尝试1: 我试过将其转换为可选
var textField : UITextField? = self as? UITextField
textField?.inputAccessoryView = toolbar
现在,它不会对UITextView的崩溃,但也没有设置任何inputAccessoryView。当我试图打印它。它在控制台上打印nil
。
println(textField?.inputAccessoryView) //It prints 'nil'
尝试2: 我想它转换为AnyObject
var textField : AnyObject = self as AnyObject
textField.inputAccessoryView = toolbar //Compile time error
如果我更换的UITextField到那么明显的UITextView它工作正常进行的UITextView但不适合的UITextField。
有什么建议吗?
1一个TextView没有文本框
至2任何物体都有inputAccessoryView
没有方法 - >> SWIFT强制类型安全
所以你不能只投对象的东西,他们不
但
从文档:
“的UIResponder类声明了两个属性输入视图和输入附件的观点:
@property(只读,保留)UIView * inputView;
@property(只读,保留)的UIView * inputAccessoryView;”
但它是只读的,有
所以检查类
var xy:AnyObject!;
if(xy.isKindOfClass(UITextField)) {
var t = xy as UITextField;
//...
}
else if(xy.isKindOfClass(UITextView)) {
var t = xy as UITextView;
//...
}
是的,但是UIResponder声明它们是只读的。我无法克服这个问题。我在UIView上创建了扩展,因为它包含在UITextField和UITextView类层次结构中。对于UIView,这些属性仍然是只读的。 – 2014-09-24 13:06:33
编辑一个简短的如果基于类切换[未经测试,但应] – 2014-09-24 13:19:54
它工作,但如何检查我的实例是否响应'setInputAccessoryView:'然后调用'setInputAccessoryView:'这种方法? – 2014-09-24 15:47:33
在斯威夫特,你可以使用type check
运算符(is
)来检查实例是否属于某个子类型。类型检查操作如果实例是该子类的实例,则为returns true
,如果不是,则为false
。
let aViewInstance : UIView = UITextView()
if aViewInstance is UITextField
{
// here, aViewInstance must be an instance of UITextField class & can't be nil
print(aViewInstance)
let textField : UITextField = aViewInstance as! UITextField
print(textField)
}
else if aViewInstance is UITextView
{
// here, aViewInstance must be an instance of UITextView class & can't be nil
print(aViewInstance)
let textView : UITextView = aViewInstance as! UITextView
print(textView)
}
else
{
print(" other object ")
}
所以你不需要检查subclass type
,使用NSObject
类的isKindOfClass
方法斯威夫特因为isKindOfClass
方法仅在NSObject的信息,并将它的子类(所有的Objective-C类)。和Swift,可以创建一个没有基类或超类的类。 例如 -
class BaseClass {
//properties and methods
}
let anObject : AnyObject = BaseClass()
if anObject is BaseClass {
print(anObject) // here, must be an instance of BaseClass, you can use it
} else {
print(" other object ")
}
一个TextView没有文本框和任何对象有没有方法inputAccessoryView - SWIFT强制类型安全 – 2014-09-23 21:13:56
是的,我知道,但我应该如何克服上述问题。我将我的开源库转换为swift https://github.com/hackiftekhar/IQKeyboardManager/blob/master/IQKeyBoardManager/IQUIView%2BIQKeyboardToolbar.m见175行 – 2014-09-23 21:17:57