從UIView屬性獲取對NSObject父項的引用

Question

我有一個(NSObject) Block *my_block作爲屬性UIView *main_view。在ViewController上，我將UIPanGestureRecognizer添加到main_view，因此手勢方法必須位於ViewController上。有沒有辦法通過手勢方法瞭解具體main_view的my_block擁有者？

這是因爲我有一個NSMutableArray的Block。在運行時將Blocks添加到NSMutableArray。

我的第一個想法是通過NSMutableArray循環比較每個main_view到識別器的UIView。另一個想法是對UIView進行分類並創建對其各自的Block的參考。但也許有一個更乾淨的方式來做到這一點。

下面是我的類和方法的一個簡單示例。

Block.h

#import <Foundation/Foundation.h> 

@interface Block : NSObject 

@property (nonatomic, strong) UIView *main_view; 

@end 

ViewController.m

#import "ViewController.h" 
#import "Block.h" 

@interface ViewController() 

@end 

@implementation ViewController 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    // the Blocks are actually added on runtime to a NSMutableArray, but this is a simpler example 

    Block *my_block = [[Block alloc] init]; 
    [[my_block main_view] addGestureRecognizer:[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]]; 
    [self.view addSubview:[my_block main_view]]; 
} 

- (void)handlePan:(UIPanGestureRecognizer *)recognizer 
{ 
    Block *block_temp = [recognizer.view ....]; 
    //recognizer.view = main_view, how to get the Block owner of this view? 
} 

Answer 1

你有Block類是target你的手勢識別器：

Block.h

@interface Block : NSObject 

@property (nonatomic, strong) UIView *main_view; 

@end 

Block.m

@implementation Block 

-(void)handleMainViewPan:(UIPanGestureRecognizer *)recognizer 
{ 
    // Now recognizer.view is the same view as self.main_view 
    // Use self as this is now your block 
} 

@end 

ViewController.m

@interface ViewController() 

@end 

@implementation ViewController 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    // the Blocks are actually added on runtime to a NSMutableArray, but this is a simpler example 

    Block *my_block = [[Block alloc] init]; 
    UIPanGestureRecognizer *gestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:my_block action:@selector(handleMainViewPan:)]; 
    [my_block.main_view addGestureRecognizer:gestureRecognizer]; 
    [self.view addSubview:my_block.main_view]; 
} 

@end 

Answer 2

相反子類的UIView你也可以使用功能：

void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy) 
id objc_getAssociatedObject(id object, const void *key) 

從docs

使用給定密鑰和關聯策略設置給定對象的關聯值。

好文章http://nshipster.com/associated-objects/

Answer 3

如果你已經有塊在陣列（我相信陣列處於ViewController屬性），你可以找到一個loop塊。

例子：

// self.blocks is NSMutableArray where blocks are stored 

- (void)handlePan:(UIPanGestureRecognizer *)recognizer 
{ 
    Block *owner = nil; 
    for (block in self.blocks) { 
     if (block.main_view == recognizer.view) { 
      owner = block; 
      break; 
     } 
    } 
}