The NSArray
and the contained NSString
objects are all immutable. There’s no way to change the objects you have.
Instead you have to create new strings and put them in a new array:
NSMutableArray *trimmedStrings = [NSMutableArray array];
for (NSString *string in arrayRefineSubjectCode) {
NSString *trimmedString = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
[trimmedStrings addObject:trimmedString];
}
arrayRefineSubjectCode = trimmedStrings;