相关疑难解决方法(0)

CoreData属性的setter是否保留？或复制价值或什么是二传手？我想知道是否必须(自动)释放我放入setter的值.

我已经做了一些快速测试.假设以下型号:

+----------+
| Class A  |
+----------+
| v :int32 |
+----------+

生成的ManagedObject然后如下所示:

//A.h
@interface A :  NSManagedObject  
{
}
@property (nonatomic, retain) NSNumber * v;
//...

//A.m
@implementation A 
@dynamic v;
...

好的,属性标记为retain,因此如果我将NSNumber设置为v,则应保留NSNumber.但它不是(我认为).我做了以下事情:

A *a = ... ;
NSNumber *retainCheck = [[NSNumber alloc] initWithInt:23];
NSLog(@"retainCheck1: %i",[retainCheck retainCount]);
a.v = retainCheck;
NSLog(@"retainCheck2: %i",[retainCheck retainCount]);
NSLog(@"retainCheck3: %i",[a.v retainCount]);
NSLog(@"pointer1: %#x",retainCheck);
NSLog(@"pointer2: %#x",a.v);

这会产生以下输出:

retainCheck1: 1
retainCheck2: 1
retainCheck3: 1
pointer1: 0x62f068
pointer2: 0x62f068

两个NSNumber都是相同的NSNumber实例(相同的指针值 - >所以它没有复制或类似的那样),并且设置器似乎不保留NSNumber.

我做的...... 我的测试错了吗？或者NSManagedObject-setters的行为与标题中描述的不一样？ …

当我使用__weak指针引用NSObject时,会显示意外的retainCount.

测试代码和结果如下图所示.

这是代码:

    id obj1 = [[NSObject alloc] init];
    id __weak obj2 = obj1;
    NSLog(@"obj1: %ld", CFGetRetainCount((__bridge CFTypeRef)obj1));        // line 31
    NSLog(@"obj2: %ld", CFGetRetainCount((__bridge CFTypeRef)obj2));        // line 32
    NSLog(@"obj1 again: %ld", CFGetRetainCount((__bridge CFTypeRef)obj1));  // line 33

所以〜我的困惑是,obj2的retainCount预计为1,为什么retainCount为2？

我从书中读到:__ weak指针将对象注册到autoreleasepool,因此保留计数+ 1.

但是,obj1和obj2指的是相同的内存地址,在这种情况下,obj1的retainCount也应该变为2.但是,它仍然保持为1.

我知道retainCount是不可靠的,但我很好奇它是如何来的.(我的环境是Xcode 8.3.3,iOS 10.3)

非常感谢任何人都可以向初学者解释这个:)

我创建了一组相同的自定义类型的对象.所有对象都具有方法showDeleteButton了hideDeleteButton.我发现当我隐藏删除按钮(删除它)按钮时,按下了retainCounter == 2.

这里的代码:

-(void)showDeleteButton {
if(!isDeleteButtonLoaded) { // Check that method was't triggered twice
    UIButton *aDeleteButton = [[UIButton alloc] initWithFrame:CGRectMake(-3, -7, 30, 29)]; // RC == 1
    [aDeleteButton setImage:[UIImage imageNamed:@"close_button.png"] forState:UIControlStateNormal];
    [self addSubview:aDeleteButton]; // RC == 2
    [aDeleteButton addTarget:self action:@selector(deleteButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
    deleteButton = aDeleteButton;
    [aDeleteButton release]; // RC == 1
    isDeleteButtonLoaded = YES;
    NSLog(@"delete button retain count (created): %d", [deleteButton retainCount]);
    [self setNeedsDisplay];
}

}

-(void)deleteButtonPressed:(id)sender {
[delegate deleteImageAtPath:self.imageFullPath];

}

-(void)hideDeleteButton {
if(isDeleteButtonLoaded) {
    NSLog(@"delete …

在这里我得到了一些丑陋的代码:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy"];
NSDate *date = [NSDate date];
NSString *textWithYear = [NSString stringWithFormat:@"text and year %@", [dateFormatter stringFromDate:date] ];
[dateFormatter release];
NSLog(@"%i", [dateFormatter retainCount]); // returns 1 !

如您所见,保留计数器返回1,我想这意味着该对象未被释放.如果我将该字符串更改为

[dateFormatter release], dateFromatter = nil;

保留计数器返回0,这应该是因为它无法计算nil的保留:)

有什么东西我不了解保留计数器,或者这个对象真的没有发布？当我release第二次发送它(努力获得零保留计数)时,它会预期粉碎:)

还有一个问题:如果dateFormatter真的被释放了,为什么当我调用[dateFormatter retainCount]时它不会崩溃？

我注意到在将我的Xcode更新为4.2之后,retainCount总是等于-1.我不在我的项目中使用ARC,我甚至尝试在项目设置中创建新项目并将ARC选项切换为关闭,但下一行的工作非常奇怪:

NSString *string = [[NSString alloc] init];
NSLog(@"%i", [string retainCount]);   //-1
[string retain];
[string retain];
[string retain];
NSLog(@"%i", [string retainCount]);   //still -1
[string release];
[string release];
[string release];
NSLog(@"%i", [string retainCount]);   //still -1

我想念一下吗？我认为如果关闭ARC选项,项目将像以前一样完全正常工作.

我需要知道retaincount对象是否应该总是0如果我想在我的代码中有一个良好的内存管理.我从一本书中得到了以下代码.并且有一个声明NSLog叫做after release = 2,那么我是否应该再释放2次以使其retaincount为0？

#import <Foundation/NSObject.h>
    #import <Foundation/NSAutoreleasePool.h>
   #import <Foundation/NSString.h>
 #import <Foundation/NSArray.h>
 #import <Foundation/NSValue.h>
 int main (int argc, char *argv[])
 {
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 NSNumber *myInt = [NSNumber numberWithInteger: 100];
 NSNumber *myInt2;
 NSMutableArray *myArr = [NSMutableArray array];
 NSLog (@”myInt retain count = %lx”,
 (unsigned long) [myInt retainCount]);
 [myArr addObject: myInt];
 NSLog (@”after adding to array = %lx”,
 (unsigned long) [myInt retainCount]);
 myInt2 = myInt;
 NSLog (@”after …

我将手动管理NSMutableDictionay的内存,而不使用自动释放.并且mutableDictonary中的每个对象都是NSArray,每次我在mutableDictionary中添加一个数组时,我将使用

NSArray *newArray = [[NSArray arrayWithArray:anArray] retain]
[mutableDict setObject:newArray forKey:@"aKey"];

问题是,我怎么能保证没有内存泄漏？我在dealloc中直接使用[mutableDict release]是好的吗？mutableDict的retainCount是否等于其对象的所有retainCounts(保留的数组)的总和？

SWIFT代码

 override func viewDidLoad() {
            super.viewDidLoad()
            var v1 = ViewController()
            let v2 = ViewController2()
            print("\(CFGetRetainCount(v1)) and \(CFGetRetainCount(v2))")
        }

在Swift引用计数打印为2和2

目标C代码

- (void)viewDidLoad {
    [super viewDidLoad];
    ViewController *v1 = [[ViewController alloc]init];
    ViewController2 *v2 = [[ViewController2 alloc]init];
    NSLog(@"%ld and %ld",CFGetRetainCount((__bridge CFTypeRef)(v1)),CFGetRetainCount((__bridge CFTypeRef)(v2)));
} 

在Objective C中,引用计数打印为1和1

为什么参考计数在目标c和swift中有所不同？

通过简单的保留/释放方案查看此代码片段:

#import <Foundation/Foundation.h>

@interface SomeClass : NSObject
@end

@implementation SomeClass
@end

int main(int argc, const char * argv[])
{
    SomeClass *aClass = [[SomeClass alloc] init];
    NSLog(@"retainCount: %lu", [aClass retainCount]);

    [aClass retain];
    NSLog(@"retainCount: %lu", [aClass retainCount]);

    [aClass release];
    NSLog(@"retainCount: %lu", [aClass retainCount]);

    [aClass release];
    NSLog(@"retainCount: %lu", [aClass retainCount]);

    return 0;
}

这是结果输出:

2013-04-29 17:33:50.695 retainCount: 1
2013-04-29 17:33:50.697 retainCount: 2
2013-04-29 17:33:50.697 retainCount: 1
2013-04-29 17:33:50.698 retainCount: 1

最后一个retainCount应为"0"或应用程序崩溃.为什么结果为"1"？!