How to return an NSMutableArray from an NSSet

问题

I'm able to put the contents of an NSSet into an NSMutableArray like this:

NSMutableArray *array = [set allObjects];

The compiler complains though because [set allObjects] returns an NSArray not an NSMutableArray. How should this be fixed?

回答1:

Since -allObjects returns an array, you can create a mutable version with:

NSMutableArray *array = [NSMutableArray arrayWithArray:[set allObjects]];

Or, alternatively, if you want to handle the object ownership:

NSMutableArray *array = [[set allObjects] mutableCopy];

回答2:

I resolved crashing by using NSMutableArray's method 'addObjectsFromArray' to assign all NSSet objects to NSMutableArray like:

[mutableArray addObjectsFromArray:[cg_Schedule.schedule_Days allObjects]];

Hope this will helps you.

回答3:

For an ordered set use:

NSArray *myArray = [[myOrderedSet array] mutableCopy];

来源：https://stackoverflow.com/questions/3826901/how-to-return-an-nsmutablearray-from-an-nsset