OOPAL is a high-level programming model for manipulating objects. It goes beyond the classic “one object at a time” model and provides a way to query and manipulate whole sets of objects at once using the principles and idioms of array programming languages. To do so, it introduces a new messaging abstraction called “message pattern”.
OOPAL, which stands for “Object-Oriented Programming and Array Languages integration”, is implemented in FScript, an open source scripting language for Cocoa.
Example: given an NSArray named “strings”, containing NSString objects, we want to create an array that contains only the strings of length less than 10.
NSMutableArray *result = [NSMutableArray array];
NSEnumerator *stringEnumerator = [strings objectEnumerator];
while (aString = [stringEnumerator nextObject])
if ([aString length] < 10)
} return result;
F-Script using OOPAL:
strings where:strings length < 10
OOPAL can be used from the F-Script environment or directly embedded inside Objective-C code (see the paper about embedding below).
Some papers and discussions about OOPAL:
As of OS 10.4 the NSPredicate class allows for a similarly concise query. Here is the updated Objective-C:
return [strings filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@”length < 10”]];
Okay, so it’s still a bit more wordy than the FScript. If it weren’t it wouldnt’ be Cocoa.