The JLTDelayOperation class is a no-op NSOperation which allows dependent
operations to delay their start.
An instance of a JLTDelayOperation is created is a delay duration. Once
started, the instance will execute for at least that duration. After the delay
has expired, the instance will finish. The instance can be cancelled any time
up until it has finished.
The simplest way to get a delay operation is create an instance.
JLTDelayOperation *delayOperation = [JLTDelayOperation delayOperationWithDelay:5.0];
The simplest way to execute the operation is to start it.
JLTDelayOperation *delayOperation = [JLTDelayOperation delayOperationWithDelay:5.0];
[delayOperation start];
This will perform a no-op operation which will finish after 5 seconds. This is useful as a way to delay the start of other operations.
JLTDelayOperation *delayOperation = [JLTDelayOperation delayOperationWithDelay:5.0];
NSOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
NSLog("perform operation");
}];
[operation addDependency:delayOperation];
NSOperationQueue *operationQueue = [[OperationQueue alloc] init];
[operationQueue addOperations:@[delayOperation, operation] waitUntilFinished:NO];
Any number of operations can be delayed by a single JLTDelayOperation.
JLTDelayOperation *delayOperation = [JLTDelayOperation delayOperationWithDelay:5.0];
NSOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{ NSLog("1"); }];
NSOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{ NSLog("2"); }];
NSOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{ NSLog("3"); }];
[operation1 addDependency:delayOperation];
[operation2 addDependency:delayOperation];
[operation3 addDependency:delayOperation];
NSOperationQueue *operationQueue = [[OperationQueue alloc] init];
[operationQueue addOperations:@[delayOperation, operation1, operation2, operation3]
waitUntilFinished:NO];
A block operation can be created with a delay using the NSBlockOperation
category method -blockOperationWithDelay:andBlock:.
NSArray *operations = [NSBlockOperation blockOperationWithDelay:5.0 andBlock:^{
NSLog("perform block operation");
}];
NSOperationQueue *operationQueue = [[OperationQueue alloc] init];
[operationQueue addOperations:operations waitUntilFinished:NO];
Notice that an array of operations is returned. The array is a pair of
operations. The first operation is a JLTDelayOperation instance, the second
operation is an NSBlockOperation instance.
An operation queue can add a block operation with a delay using the
NSOperationQueue category method -addOperationWithDelay:andBlock:.
NSOperationQueue *operationQueue = [[OperationQueue alloc] init];
JLTDelayOperation *delayOperation = [operationQueue addOperationWithDelay:5.0 andBlock:^{
NSLog("perform block operation");
}];
Here a JLTDelayOperation instance is returned. This instance can be used to
add multiple operations to the operation queue using the category method
-addOperationDependentOnOperation:withBlock:.
NSOperationQueue *operationQueue = [[OperationQueue alloc] init];
JLTDelayOperation *delayOperation = [operationQueue addOperationWithDelay:5.0 andBlock:^{
NSLog("1");
}];
[operationQueue addOperationDependentOnOperation:delayOperation withBlock:^{
NSLog("2");
};
[operationQueue addOperationDependentOnOperation:delayOperation withBlock:^{
NSLog("3");
};
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