对于委托的__unsafe_unretained将无法构建 [英] __unsafe_unretained for a delegate won't build

问题描述

我从.h文件获得此代码（代码段）：

I have this code (snippet) from a .h file:

#import <UIKit/UIKit.h>
#import "ILView.h"

/**
 * Controls the orientation of the picker
 */
typedef enum {
    ILHuePickerViewOrientationHorizontal     =   0,
    ILHuePickerViewOrientationVertical       =   1
} ILHuePickerViewOrientation;

@class ILHuePickerView;

/**
 * Hue picker delegate
 */
@protocol ILHuePickerViewDelegate

/**
 * Called when the user picks a new hue
 *
 * @param hue 0..1 The hue the user picked
 * @param picker The picker used
 */
-(void)huePicked:(float)hue picker:(ILHuePickerView *)picker;

@end

/**
 * Displays a gradient allowing the user to select a hue
 */
@interface ILHuePickerView : ILView {
    id<ILHuePickerViewDelegate> delegate;
    float hue;
    ILHuePickerViewOrientation pickerOrientation;
}

/**
 * Delegate
 */
//@property (assign, nonatomic) IBOutlet id<ILHuePickerViewDelegate> delegate;
@property (assign, nonatomic) IBOutlet __unsafe_unretained id<ILHuePickerViewDelegate> delegate;

/**
 * The current hue
 */
@property (assign, nonatomic) float hue;

.m文件如下所示：

#import "ILHuePickerView.h"
#import "UIColor+GetHSB.h"

@interface ILHuePickerView(Private)

-(void)handleTouches:(NSSet *)touches withEvent:(UIEvent *)event;

@end

@implementation ILHuePickerView

@synthesize color, delegate, hue, pickerOrientation;

#pragma mark - Setup

-(void)setup
{
    [super setup];

我在SO上查找类似案例，看到我需要在物业中加入__unsafe_unretained ...我做到了（希望是正确的），但它仍然无法构建。完整的错误消息是：具有assign属性的属性'delegate'的现有ivar'委托'必须是__unsafe_unretained

I looked on SO for similar cases, and saw that I needed to put "__unsafe_unretained" in the property... I did that (hopefully correct), but it still fails on the build. The full error message is: Existing ivar 'delegate' for property 'delegate' with assign attribute must be __unsafe_unretained

我做错了什么？

推荐答案

正如错误消息告诉您的那样， ivar ：

As the error message is telling you, the ivar:

@interface ILHuePickerView : ILView {
    id<ILHuePickerViewDelegate> delegate;    // <-- This is the ivar

需要声明 __ unsafe_unretained ：

__unsafe_unretained id<ILHuePickerViewDelegate> delegate;

不属性：

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

因为ARC所有权限定符不适用于属性;它们只适用于变量。

because the ARC ownership qualifiers don't apply to properties; they only apply to variables.

由于 @synthesize 指令创建了 ivar for你（使用正确的ARC限定符），但是，你可以跳过它的声明：

Since the @synthesize directive creates the ivar for you (with the correct ARC qualifier), however, you can just skip its declaration:

@interface ILHuePickerView : ILView 

/**
 * Delegate
 */
@property (assign, nonatomic) IBOutlet id<ILHuePickerViewDelegate> delegate;

// etc.

实际上，现在是推荐程序;参见定义类。

Which is, in fact, now the recommended procedure; see Defining Classes in TOCPL.

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