在Objective C中有一个类似NSArray,NSDictionary等类的可变和不可变版本的逻辑是什么？

NSArray *immutableArray = @[@1, @2, @3];
NSMutableArray *mutableArray = [immutableArray mutableCopy];

NSDictionary *immutableDictionary = @{@"key1": @"value1", @"key2": @"value2"};
NSMutableDictionary *mutableDictionary = [immutableDictionary mutableCopy];

NSSet *immutableSet = [NSSet setWithObjects:@1, @2, @3, nil];
NSMutableSet *mutableSet = [immutableSet mutableCopy];

NSMutableArray *mutableArray = [NSMutableArray arrayWithObjects:@1, @2, @3, nil];
NSArray *immutableArray = [NSArray arrayWithArray:mutableArray];

NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];
NSDictionary *immutableDictionary = [NSDictionary dictionaryWithDictionary:mutableDictionary];

NSMutableSet *mutableSet = [NSMutableSet setWithObjects:@1, @2, @3, nil];
NSSet *immutableSet = [NSSet setWithSet:mutableSet];