objective-c - copy、mutableCopy 和赋值有什么区别？

Question

我以为我理解了 copy 和 mutableCopy 之间的区别。但今天我对自己产生了怀疑。我还是不太明白。

NSArray *arrayB = [NSArray arrayWithObject:@"a"];
NSArray *arrayA = [arrayB copy];
NSArray *arrayC = [arrayB mutableCopy];
NSArray *arrayD = arrayB;

当我对 arrayA、arrayC 或 arrayD 进行一些更改时，arrayB 是否会与更改后的 arrayA、arrayC 和 arrayD 之一发生相同的更改？

Answer 1

// Can't modify this NOW
NSArray *arrayB = [NSArray arrayWithObject:@"a"]; 

// Create another copy of Array B like XEROX. If you change in XEROX 
// it does not reflect to original Copy
NSArray *arrayA = [arrayB copy]; 

// This is a mutable copy so you can make changes in this and you have
// to change NSArray to NSMutableArray here as it the mutable copy.
NSMutableArray *arrayC = [arrayB mutableCopy]; 

// Any change made in arrayD reflect to arrayB but arrayD is NSArray
// (immutable) so you can not make any changes in arrayD
NSArray *arrayD = arrayB;

希望这能帮助您解决问题。