Get all methods of an Objective-C class or instance

NSObject.m

// Either in lldb:
(lldb) po [self _methodDescription]

//or in code:

@interface NSObject (Private)
- (NSString*)_methodDescription;
@end

// Somewhere in the code:
NSLog(@"%@", [objectToInspect performSelector:@selector(_methodDescription)]);

//**
Output will look as following:

<__NSArrayM: 0x7f9 ddc4359a0>:
in __NSArrayM:
    Class Methods:
        + (BOOL) automaticallyNotifiesObserversForKey:(id)arg1; (0x11503b510)
        + (id) allocWithZone:(_NSZone*)arg1; (0x11503b520)
        + (id) __new:::::(const id*)arg1; (0x114f0d700)
    Instance Methods:
        - (void) removeLastObject; (0x114f669a0)
        - (void) dealloc; (0x114f2a8f0)
        - (void) finalize; (0x11503b2c0)
        - (id) copyWithZone:(_NSZone*)arg1; (0x114f35500)
        - (unsigned long) count; (0x114f0d920)
        - (id) objectAtIndex:(unsigned long)arg1; (0x114f2a730)
        - (void) getObjects:(id*)arg1 range:(_NSRange)arg2; (0x114f35650)
        - (void) addObject:(id)arg1; (0x114f0d8e0)
        - (void) setObject:(id)arg1 atIndex:(unsigned long)arg2; (0x114f99680)
        - (void) insertObject:(id)arg1 atIndex:(unsigned long)arg2; (0x114f0d940)
        - (void) exchangeObjectAtIndex:(unsigned long)arg1 withObjectAtIndex:(unsigned long)arg2; (0x114f8bf80)
        ......
in NSMutableArray:
    Class Methods:
        + (id) copyNonRetainingArray; (0x11ee20178)
        + (id) nonRetainingArray; (0x11ee201e8)
        + (id) nonRetainingArray; (0x120475026)
        + (id) arrayWithCapacity:(unsigned long)arg1; (0x114f74280)
        ......
*/