uipickerview不显示

我在uiview上有一个uipickerview。我已经在.h和.m文件中实现了它的协议:

 <UIPickerViewDataSource, UIPickerViewDelegate>

在ib中,我已经将上面的连接到选择器上,这个选择器也有一个iboutlet。方法如下:

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)thePickerView {
return 1;
}

- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component {
return [self.arr count];
}

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row  forComponent:(NSInteger)component {
return @"test";
}

- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
//do something
}

有什么想法能让我找不到哪一块来工作吗?