Support file for Inside the Bracket part 7, adding some methods to classes at runtime.

addstuff.m

// Add some methods with the runtime.

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

// clang -g -fobjc-arc -Wall -framework Foundation -o addstuff addstuff.m

@interface Glorn : NSObject
@end

@implementation Glorn

+ (BOOL) resolveInstanceMethod: (SEL) selector {
    // Refuse this one so we get the "nobody here" exception.
    if (sel_isEqual(selector, @selector(larvoid))) return NO;

    // Don't want to handle anything that takes arguments.
    if (strchr(sel_getName(selector), ':')) return NO;

    IMP blockImp =
        imp_implementationWithBlock ((__bridge void *) ^(id self) {
                NSLog (@"you just called %@",
                       NSStringFromSelector(selector));
        });

    class_addMethod ([self class], selector, blockImp, "v@:");

    return YES;

} // resolveInstanceMethod

@end


@interface Glorn (HushTheCompiler)
- (NSString *) larvoid;
- (NSString *) greetingWithCount: (NSUInteger) count;
- (void) keep;
- (void) watching;
- (void) theSkies;
@end


static NSString *Larvoid (id self, SEL _cmd) {
    return @"Zogg";
} // Larvoid


void AddSomeMethods (void) {
    Glorn *glorn = [Glorn new];

    NSString *name;

    // See that it breaks;
    @try {
        name = [glorn larvoid];
    }
    @catch (id thing) {
        NSLog (@"got expected exception");
    }

    // Add a method with a function pointer
    Class glornClass = [Glorn class];
    
    BOOL success = class_addMethod (glornClass, @selector(larvoid), (IMP)Larvoid, "@:v");
    if (!success) {
        printf ("phooey, couldn't add method\n");
        return;
    }

    name = [glorn larvoid];
    NSLog (@"Hello my name is %@", name);

    // Add a method with a block

    IMP blockImp =
        imp_implementationWithBlock ((__bridge void *)
                                     ^(id self, NSUInteger count) {
            for (NSUInteger i = 0; i < count; i++) {
                NSLog (@"Hello #%ld, %@", i, name);
            }
        });

    char *encoding;
    asprintf(&encoding, "v@:%s", @encode(NSUInteger));
    success = class_addMethod (glornClass, @selector(greetingWithCount:),
                               blockImp, encoding);
    free (encoding);
    if (!success) {
        printf ("lame, couldn't add the block imp\n");
        return;
    }

    [glorn greetingWithCount: 5];

    [glorn keep];
    [glorn watching];
    [glorn theSkies];

} // AddSomeMethods


int main (void) {
    @autoreleasepool {
        AddSomeMethods ();
    }

    return 0;

} // void


#if 0
-[Glorn larvoid]: unrecognized selector sent to instance 0x1050142b0
got expected exception
Hello my name is Zogg
Hello #0, Zogg
Hello #1, Zogg
Hello #2, Zogg
Hello #3, Zogg
Hello #4, Zogg
you just called who
you just called goes
you just called there
you just called _doZombieMe

(_doZombieMe was totally unexpected)

#0  +[Glorn resolveInstanceMethod:] (self=0x100003518, _cmd=0x7fff8cf433d3, selector=0x7fff8b59ec3c) at addstuff.m:23
#1  0x00007fff8a38db9b in _class_resolveMethod ()
#2  0x00007fff8a38b35e in lookUpMethod ()
#3  0x00007fff8a38da5c in class_respondsToSelector ()
#4  0x00007fff8b44d051 in -[NSObject dealloc] ()
#5  0x00000001000016f6 in AddSomeMethods () at addstuff.m:93
#6  0x000000010000189d in main () at addstuff.m:100

#endif