Question

I want to get some objects from array contains objects where one of objects property satisfy the condition

Like in c#

example :

NSMutablearray * coursesinfo ;

this array contain more than 30 courses

course is object on of its property is finalgrade

i want to get all courses where final grade < 100

can i do this in objective -c like c# ? and how?

Answer 1

the where statement is like using a predicate in cocoa/cocoa touch. here is an example, where I have an array of image file names from a directory and I am looking for the base file name. The indexesOfObjectsWithOptions: method returns a set of Indices that pass the specific test. NSEnumerationConcurrent utilizes a concurrent queue to take advantage of multiple cores, if present.

NSIndexSet *indexSet=[allImageURLs indexesOfObjectsWithOptions:NSEnumerationConcurrent passingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    BOOL match=NO;
    NSRange twoXRange=[((NSURL *)obj).absoluteString rangeOfString:@"@2x"];
    NSRange iPhoneRange=[((NSURL *)obj).absoluteString rangeOfString:@"~ipad"];
    if (twoXRange.location==NSNotFound && iPhoneRange.location==NSNotFound) {
        match=YES;
    }
    return  match;
}];

self.imageURLs=[allImageURLs objectsAtIndexes: indexSet];

for your particular case I would do the following:

NSIndexSet *theSet=[coursesinfo indexesOfObjectsWithOptions:NSEnumerationConcurrent passingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    BOOL match=NO;

    if( obj.finalGrade<100 ){
       match=YES;
    }
    return match;
}];

NSArray *courses=[coursesinfo objectsAtIndexes: theSet];

Good luck!

t