Question

我开发了一个类别，它使NSOperation能够以定时间隔在后台执行。我真的很感激收到一些反馈意见，尤其是这种方法的任何潜在问题，我都没有想到。

谢谢！

以下是代码：

的NSOperation + Repeat.h

#import <Foundation/Foundation.h>

@interface NSOperation (repeat)

@property (readonly, nonatomic) NSTimeInterval repeatInterval;
@property (readonly, nonatomic) NSOperationQueue *repeatOperationQueue;

- (void)performUsingOperationQueue:(NSOperationQueue *)operationQueue;
- (void)performAtRepeatingInterval:(NSTimeInterval)interval usingOperationQueue:(NSOperationQueue *)operationQueue;

@end

的NSOperation + Repeat.m

#import "NSOperation+repeat.h"
#import <objc/runtime.h>

static char const * const RepeatPropertiesKey = "RepeatProperties";

@implementation NSOperation (repeat)

@dynamic repeatInterval;
@dynamic repeatOperationQueue;

static NSString * RepeatIntervalKey = @"interval";
static NSString * RepeatOperationQueueKey = @"operationQueue";
static NSString * RepeatTimerKey = @"timer";

- (NSMutableDictionary *)repeatProperties {
    NSMutableDictionary * properties = objc_getAssociatedObject(self, RepeatPropertiesKey);
    if (properties == nil) {
        properties = [NSMutableDictionary new];
        objc_setAssociatedObject(self, RepeatPropertiesKey, properties, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return properties;
}

- (NSTimeInterval)interval {
    NSNumber * interval = [[self repeatProperties] objectForKey:RepeatIntervalKey];
    return [interval doubleValue];
}

- (NSOperationQueue *)repeatOperationQueue {
    NSOperationQueue * operationQueue = [[self repeatProperties] objectForKey:RepeatOperationQueueKey];
    return operationQueue;
}

- (void)performUsingOperationQueue:(NSOperationQueue *)operationQueue {
    [operationQueue addOperation:[self copy]];
}

- (void)performAtInterval:(NSTimer *)timer {
    [self performUsingOperationQueue:self.repeatOperationQueue];
}

- (void)performAtRepeatingInterval:(NSTimeInterval)interval usingOperationQueue:(NSOperationQueue *)operationQueue {
    // Save interval and operationQueue in repeatProperties
    [self.repeatProperties setValue:[NSNumber numberWithDouble:interval] forKey:RepeatIntervalKey];
    [self.repeatProperties setValue:operationQueue forKey:RepeatOperationQueueKey];

    // Create timer to call performAtInterval on self
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:(interval*60)
                                                      target:self
                                                    selector:@selector(performAtInterval:)
                                                    userInfo:nil
                                                     repeats:YES];

    // Save the timer in repeatProperties
    [self.repeatProperties setValue:timer forKey:RepeatTimerKey];

    [self performUsingOperationQueue:operationQueue];
}

@end

以下是可以重复的NSOperation子类的示例：

MSScheduleImportOperation.h

#import <Foundation/Foundation.h>
#import "NSOperation+Repeat.h"

@interface MSScheduleImportOperation : NSOperation <NSCopying>

@property (readonly, strong, nonatomic) NSString* employeeId;

- (id)initWithEmployeeId:(NSString *)employeeId;

@end

MSScheduleImportOperation.m

#import "MSScheduleImportOperation.h"

@implementation MSScheduleImportOperation

@synthesize employeeId = __employeeId;

- (id)initWithEmployeeId:(NSString *)employeeId     {
    self = [super init];
    __employeeId = [employeeId copy];
    return self;
}

- (id)copyWithZone:(NSZone *)zone {
    MSScheduleImportOperation* copy = [[MSScheduleImportOperation alloc] initWithEmployeeId:self.employeeId];
    return copy;
}

- (void)main
{
 ...   
}


@end

Answer 1

Apple documentation说：

操作对象是单击对象 - 也就是说，它执行一次任务，不能再用来执行它。

所以第一个问题是可能有内部因素阻止它工作。虽然，我看到你试图通过复制来解决问题。

这导致我们另一个问题是NSOperation未宣传符合NSCopying。

[operationQueue addOperation:[self copy]];

这一行应该抛出异常。

Answer 2

而不是NSOperation上的对象复制自身并将副本添加到NSOperationQueue的类别 - 在更高级别管理它会更简单。例如：

+[RepeatingOperation operationBlock:(InitOperationBlock)operationBlock
                              queue:(NSOperationQueue*)queue
                           interval:(NSTimeInterval)interval];

其中InitOperationBlock将是创建和配置操作的块。

主要的好处是API会更难搞乱。例如，在原始帖子的类别中，如果您忘记设置performUsingOperationQueue:，repeatOperationQueue将无声地失败。

NSOperation与重复选项

2 个答案: