NSOperation with repeat option

Question

我開發了一個類別，它給NSOperation在後臺定時執行的能力。我真的很感激在這方面得到一些反饋，特別是我沒有想到的這種方法的任何潛在問題。

謝謝！

下面的代碼：

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 

下面介紹了可重複的NSOperation子類的一個例子：

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

的Apple documentation說：

的操作對象爲單次對象，也就是說，它一旦執行其任務，不能用於執行它再次。

所以第一個問題是可能有內部元件阻止它工作。雖然，我看到你試圖通過複製來解決問題。

這導致我們的另一個問題是NSOperation未被標榜爲符合NSCopying。

[operationQueue addOperation:[self copy]]; 

此行應該引發異常。

Answer 2

而不是NSOperation上的類別，其中對象複製自身並將副本添加到NSOperationQueue - 在較高級別管理該對象會更簡單。例如：

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

其中InitOperationBlock將是創建和配置操作的塊。

最主要的好處是API很難搞砸。例如，如果您忘記設置repeatOperationQueue，則在原始帖子的類別中，performUsingOperationQueue:將自動失敗。