ios - 为动态创建的 UIPickerView 添加协议(protocol)

Question

这个问题与此相关SO question (please see accepted answer) 。我将 UIPickerView 添加到未在其界面中添加 UIPickerViewDelegate 或 UIPickerViewDataSource 协议(protocol)的 View 。但是，UIPickerView 对象所需的所有方法都已正确实现，并且程序使用这些委托(delegate)运行良好:

pv.delegate = self;
pv.dataSource = self;    

由于类接口(interface)中没有添加协议(protocol)，因此 Xcode 会相应地抛出这两个警告:

Assigning to 'id<UIPickerViewDelegate>' from incompatible type
Assigning to 'id<UIPickerViewDataSource>' from incompatible type

此代码似乎添加了所需的协议(protocol)，并且一旦为选取器 View 委托(delegate)和数据源属性分配了新创建的委托(delegate)类，警告就会停止。delegateClass。

UIPickerView *pv = [[UIPickerView alloc] initWithFrame:CGRectMake(x, y, width, height)];

Class<UIPickerViewDelegate, UIPickerViewDataSource> delegatedClass = (Class<UIPickerViewDelegate, UIPickerViewDataSource>)[self class];

pv.delegate = delegatedClass;
pv.dataSource = delegatedClass;

但是，即使没有错误，程序也会崩溃。

也许是实现或分配错误？

更新: 错误的屏幕截图

Answer 1

您正在尝试将一个类设置为委托(delegate)。请设置一个实例来解决此问题。

UIPickerView *pv = [[UIPickerView alloc] initWithFrame:CGRectMake(x, y, width, height)];
pv.delegate = self;

代替

UIPickerView *pv = [[UIPickerView alloc] initWithFrame:CGRectMake(x, y, width, height)];

Class<UIPickerViewDelegate, UIPickerViewDataSource> delegatedClass = (Class<UIPickerViewDelegate, UIPickerViewDataSource>)[self class];

pv.delegate = delegatedClass;

在定义您的自定义委托(delegate)协议(protocol)时仅使用

@property(nonatomic,assign)id delegate;

代替

@property(nonatomic,assign)id<YOUR_PROTOCOL> delegate;