Question

我试图使用单例概念来保留GPS信息，但我不知道问题出在哪里，我的变量只显示为零。

Singleton.h：

@interface Singleton : NSObject

@property (readwrite) NSString *propertyA;
@property (readwrite) NSString *propertyB;
@property (readwrite) NSString *propertyC;

+ (Singleton *)sharedInstance;

@end

Singleton.m：

#import "Singleton.h"

@interface Singleton ()
{
    NSString *variableA;
    NSString *variableB;
    NSString *variableC;
}
@end

@implementation Singleton

static Singleton *sharedInstance = nil;

+ (Singleton *)sharedInstance
{
    @synchronized(self) {
        if (sharedInstance == nil) {
            sharedInstance = [[Singleton alloc] init];
        }
    }
    return sharedInstance;
}

+ (id)allocWithZone:(NSZone *)zone {
    @synchronized(self) {
        if (sharedInstance == nil) {
            sharedInstance = [super allocWithZone:zone];
            return sharedInstance;
        }
    }
    return nil;
}

- (id)init
{
    self = [super init];
    if (self)
    {
        variableA = nil;
        variableB = nil;
        variableC = nil;
    }
    return self;
}

@end

OverlayViewController.m中的

：

#import "Singleton.h"

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
        NSLog(@"didUpdateToLocation: %@", newLocation);
        CLLocation *currentLocation = newLocation;

        if (currentLocation != nil) {
            _longitudeLabel.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude];
            _latitudeLabel.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude];
        }

        // Setting properties
        NSString *variableA = _latitudeLabel.text;
        [[Singleton sharedInstance] setPropertyA:variableA];      
}

然后我再回想一下这个价值......

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
     NSString *variableA = [[Singleton sharedInstance] propertyA];    
     NSLog(@"Latitude = %.8f", variableA);
}

感谢瑞吉斯

Answer 1

我的第一个猜测是你在任何地方都没有@synthesize，所以没有setter / getters

如果这不起作用，那么你应该将你的变量声明移动到你的.h文件中，我不明白为什么你会在你的.m上使用它们

我指的是：

@interface Singleton ()
{
    NSString *variableA;
    NSString *variableB;
    NSString *variableC;
}
@end

修改处理单身人士时的两个好习惯：

1）在您的方法中声明您的static ClassName *singleton，以便您班级中的其他方法无法直接访问它，并且需要使用[[self class] sharedInstance];
来请求它
2）使用dispatch_once进行线程安全

+ (FooBar *)sharedInstance { static dispatch_once_t pred; static FooBar *_sharedInstance = nil; dispatch_once(&pred, ^{ _sharedInstance = [[[self class] alloc] init]; }); return _sharedInstance; }

Answer 2

@property (readwrite) NSString *propertyA;
@property (readwrite) NSString *propertyB;
@property (readwrite) NSString *propertyC;

我猜上面的变量没有setter和getter，意味着你需要@synthesize它们。

这就是为什么下面的代码没有设置PropertyA值。

[[Singleton sharedInstance] setPropertyA:variableA];

单身价值仍为零

2 个答案: