xcode IOS：给@selector 添加一个参数
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IOS: add a parameter to @selector
提问by cyclingIsBetter
When I have this line of code
当我有这行代码时
UILongPressGestureRecognizer *downwardGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(dragGestureChanged:)];
and this
和这个
- (void)dragGestureChanged:(UILongPressGestureRecognizer*)gesture{
...
}
I want to add at "@selector(dragGestureChanged:)" a parameter that is "(UIScrollView*)scrollView", how can I do?
我想在“@selector(dragGestureChanged:)”处添加一个“(UIScrollView*)scrollView”参数，我该怎么做？
回答by Tommy
You can't directly — UIGestureRecognizers know how to issue a call to a selector that takes one argument only. To be entirely general you'd probably want to be able to pass in a block. Apple haven't built that in but it's fairly easy to add, at least if you're willing to subclass the gesture recognisers you want to get around the issue of adding a new property and cleaning up after it properly without delving deep into the runtime.
你不能直接 — UIGestureRecognizers 知道如何调用只接受一个参数的选择器。为了完全通用，您可能希望能够传入一个块。Apple 还没有内置它，但它很容易添加，至少如果你愿意将手势识别器子类化，你想要解决添加新属性并在它之后正确清理的问题，而无需深入研究运行时.
So, e.g. (written as I go, unchecked)
所以，例如（随我写，未选中）
typedef void (^ recogniserBlock)(UIGestureRecognizer *recogniser);
@interface UILongPressGestureRecognizerWithBlock : UILongPressGestureRecognizer
@property (nonatomic, copy) recogniserBlock block;
- (id)initWithBlock:(recogniserBlock)block;
@end
@implementation UILongPressGestureRecognizerWithBlock
@synthesize block;
- (id)initWithBlock:(recogniserBlock)aBlock
{
self = [super initWithTarget:self action:@selector(dispatchBlock:)];
if(self)
{
self.block = aBlock;
}
return self;
}
- (void)dispatchBlock:(UIGestureRecognizer *)recogniser
{
block(recogniser);
}
- (void)dealloc
{
self.block = nil;
[super dealloc];
}
@end
And then you can just do:
然后你可以这样做：
UILongPressGestureRecognizer = [[UILongPressGestureRecognizerWithBlock alloc]
initWithBlock:^(UIGestureRecognizer *recogniser)
{
[someObject relevantSelectorWithRecogniser:recogniser
scrollView:relevantScrollView];
}];
回答by trojanfoe
So the method will look like this:
所以该方法将如下所示：
- (void)dragGestureChanged:(UILongPressGestureRecognizer*)gesture
scrollView:(UIScrollView *)scrollview
{
...
}
The selector will look like this:
选择器将如下所示：
UILongPressGestureRecognizer *downwardGesture = [[UILongPressGestureRecognizer alloc]
initWithTarget:self action:@selector(dragGestureChanged:scrollView:)];
