Friday, May 31, 2013

NSArray enumerateObjectsWithOptions example in Objective C (iOS).

NSArray enumerateObjectsWithOptions

Executes a given block using each object in the array.

- (void)enumerateObjectsWithOptions:(NSEnumerationOptions)opts usingBlock:(void (^)(id obj, NSUInteger idx, BOOL *stop))block

Parameters of [NSArray enumerateObjectsWithOptions]
A bit mask that specifies the options for the enumeration (whether it should be performed concurrently and whether it should be performed in reverse order).
The block to apply to elements in the array.
The block takes three arguments:
The element in the array.
The index of the element in the array.
A reference to a Boolean value. The block can set the value to YES to stop further processing of the array. The stop argument is an out-only argument. You should only ever set this Boolean to YES within the Block.

Discussion of [NSArray enumerateObjectsWithOptions]
By default, the enumeration starts with the first object and continues serially through the array to the last object. You can specify NSEnumerationConcurrent and/or NSEnumerationReverse as enumeration options to modify this behavior.

NSArray enumerateObjectsWithOptions example.
NSMutableArray *array = [[rows] objectForKey:statementType];
[[array copy] enumerateObjectsWithOptions: NSEnumerationReverse
    usingBlock:^(id coaItem, NSUInteger idx, BOOL *stop) {
    if ([self objectIsTooUglyToExist:coaItem])
        [array removeObjectAtIndex:idx];

Example of [NSArray enumerateObjectsWithOptions].
NSMutableArray *newArray = [[NSMutableArray alloc] initWithCapacity:[myArray count]];
__block newArray;
[myArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

 double aValue = [obj doubleValue];                     
 aValue += 90.0;
 [newArray insertObject:[NSNumber numberWithDouble:aValue] atIndex:idx];

NSArray enumerateObjectsWithOptions example.
[myArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id obj, NSUInteger idx, BOOL *stop)
    double aValue = [obj doubleValue];                     
    aValue += 90.0;
    [myArray replaceObjectAtIndex:idx withObject:[NSNumber numberWithDouble:aValue]];

End of NSArray enumerateObjectsWithOptions example article.