投稿者: moware

#import <Foundation/NSObject.h>
#import <stdio.h>

@interface A : NSObject
- (void)whoAreYou;
@end

@implementation A
- (void)whoAreYou { printf("I'm A\n"); }
@end

@interface B : NSObject
- (void)whoAreYou;
@end

@implementation B
- (void)whoAreYou { printf("I'm B\n"); }
@end

int main(void)
{
    id obj;
    int n;

    scanf("%d", &n);
    switch (n) {
    case 0:  obj = [[A alloc] init]; break;
    case 1:  obj = [[B alloc] init]; break;
    case 2:  obj = [[NSObject alloc] init]; break;
    }
    [obj whoAreYou];
    return 0;
}

1
I'm B

2
2023-10-16 10:28:08.551 dyna[12438:464557] -[NSObject whoAreYou]: unrecognized selector sent to instance 0x600002a70000
2023-10-16 10:28:08.552 dyna[12438:464557] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSObject whoAreYou]: unrecognized selector sent to instance 0x600002a70000'
*** First throw call stack:
(
	0   CoreFoundation                      0x00000001aac0b104 __exceptionPreprocess + 176
	1   libobjc.A.dylib                     0x00000001aa729fd0 objc_exception_throw + 60
	2   CoreFoundation                      0x00000001aacb210c -[NSObject(NSObject) __retain_OA] + 0
	3   CoreFoundation                      0x00000001aab73030 ___forwarding___ + 1600
	4   CoreFoundation                      0x00000001aab72930 _CF_forwarding_prep_0 + 96
	5   dyna                                0x00000001026efefc main + 176
	6   dyld                                0x00000001aa75bf28 start + 2236
)
libc++abi: terminating due to uncaught exception of type NSException
Abort trap: 6

#import <Foundation/NSObject.h>
#import <stdio.h>

@interface A: NSObject
- (void)method1;
- (void)method2;
@end

@implementation A
- (void)method1 { printf("method1 of Class A\n"); }
- (void)method2 { printf("method2 of Class A\n"); }
@end

@interface B: A
- (void)method2;
@end

@implementation B
- (void)method2 {
    printf("method2 of Class B\n");
    printf("self --> ");
    [self method1];
    printf("super--> ");
    [super method2];
}
@end

@interface C: B
- (void)method1;
@end

@implementation C
- (void)method1 { printf("method1 of Class C\n"); }
@end

int main(void)
{
    id x = [[B alloc] init];
    id y = [[C alloc] init];
    printf("--- instance of B ---\n");
    [x method1];
    [x method2];
    printf("--- instance of C ---\n");
    [y method1];
    [y method2];
    return 0;
}

--- instance of B ---
method1 of Class A
method2 of Class B
self --> method1 of Class A
super--> method2 of Class A
--- instance of C ---
method1 of Class C
method2 of Class B
self --> method1 of Class C
super--> method2 of Class A // 循環にならない

#import "Volume.h"

@implementation Volume
- (id)initWithMin:(int)a max:(int)b step:(int)s
{
    self = [super init];
    if (self != nil) {
        val = min = a;
        max = b;
        step = s;
    }
    return self;
}

- (int)value
{
    return val;
}

- (id)up
{
    if ((val += step) > max)
        val = max;
    return self;
}

- (id)down
{
    if ((val -= step) < min)
        val = min;
    return self;
}
@end

#import "HelloWorldAppDelegate.h"

@implementation HelloWorldAppDelegate

@synthesize window;

- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after application launch
    window.rootViewController = [UIViewController new]; // この行を追加
    [window makeKeyAndVisible];
}

- (void)dealloc {
    [window release];
    [super dealloc];
}

@end