what is difference between alloc and allocWithZone:?

what is difference between alloc and allocWithZone:?

objective-c memory-management alloc

objective-c

Lazy instantiation in Objective-C/ iPhone development

objective-c properties initialization lazy-initialization alloc

objective-c

Objective-C asking for alloc on swift class

objective-c swift alloc

objective-c

Automatic Reference Counting Issue: Assigning retained object to unsafe_unretained variable; object will be released after assignment

objective-c object automatic-ref-counting alloc

objective-c