The comp.lang.objective-C FAQ listing

header files

// this is a BCPL-style comment
/* this is a C comment
 * it spans multiple lines
 * note that comments of this type cannot be nested!
 */
-(id)init {
  if((self=[super init])) { // invoke superclass -init
    someIvar=[[MyClass alloc] init];
  }
  return self; //i.e. return this object
}
MyClass *someObject=[[MyClass alloc] init];
id aClass=[someObject class];
struct MyClass_t {
  @defs(MyClass)
};
@interface ClassName (CategoryName)
-method;
@end
@implementation ClassName (CategoryName)
-method {...}
@end
@protocol ProtocolName
-method;
@end
@protocol ProtocolName <ParentProtocol>
@interface ClassName <ProtocolName>
@interface MyClass : NSObject <AProtocol>
[obj conformsTo:@protocol(ProtocolName)]
[obj conformsToProtocol:@protocol(ProtocolName)]
id <ProtocolName> obj;
ClassName <ProtocolName> *obj;
SEL aSelector=@selector(doSomethingWithStuff:);
id (*IMP)(id, SEL, ...);
IMP imp=[obj methodForSelector:@selector(message)];
IMP imp=[obj methodFor:@selector(message)];
id anObject, theResult;
IMP someImp;
SEL aSelector;
// ...
theResult=someImp(anObject,aSelector);
int (*foo)(id,SEL);
int result;
foo=(int(*)(id,SEL))[anArray methodForSelector:@selector(count)];
result=foo(anArray,@selector(count));
        typedef int (*IntReturn)(id,SEL);
	NSArray *ary=[NSArray alloc];
	SEL initSel=@selector(initWithObjects:),countSel=@selector(count);
	//id returned here
	ary=objc_msgSend(ary,initSel,@"Hello",@"World",nil);
	//int returned here
	c=((IntReturn)objc_msgSend)(ary,countSel);
	NSLog(@"%@: %d",ary,c);

        NSArray *ary=[[NSArray alloc] initWithObjects:@"Hello",@"World",nil];
        int *cp;
        SEL countSel=@selector(count);
        Method_t meth=class_get_instance_method([ary class],countSel);
        arglist_t frame=objc_calloc(8,1);
        const char *rettype=objc_skip_type_qualifiers(meth->method_types);
        int stackargs=atoi(objc_skip_typespec(rettype));
        frame->arg_ptr=stackargs?objc_calloc(stackargs,1):0;
        cp=(int *)objc_msg_sendv(ary,countSel,frame);
        NSLog(@"%@: %d",ary,*cp);

@try {
  //code which may cause an exception to be thrown
  ...
}
@catch(MyExceptionClass *ex) {
  // handle a custom exception
  ...
}
@catch(id *ex) {
  // generic exception handler
  ...
}
@finally {
  // this will happen whether or not an exception occurred.
  ...
} 
@synchronized(object) {
  ...
}
[[object getLock] lock];
...
[[object getLock] unlock];
gcc -c myfile.m -lobjc
gcc -framework Cocoa -c myfile.m
NSArray *bar=...;
for (id foo in bar)
{
  [foo doSomething];
}

NSArray *bar=...;
NSEnumerator *e=[bar objectEnumerator];
id foo;
while(foo=[e nextObject])
{
  [foo doSomething];
}

#import <Foundation/NSObject.h>
@interface CollectionTrampoline : NSProxy
{
	id theCollection;
}
- (id)initOnCollection:(id)aCollection;
@end

- (id)initOnCollection:(id)aCollection
{
	theCollection=[aCollection retain];
	return self;
}

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

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
  NSMethodSignature *sig = nil;

  if([theCollection count])
    sig = [[theCollection objectAtIndex:0] methodSignatureForSelector:aSelector];

  if(!sig)
    sig = [NSObject instanceMethodSignatureForSelector:@selector(release)];

   return sig;
}

- (void)forwardInvocation:(NSInvocation *)anInv
{
	id i;
	NSEnumerator *en=[theCollection objectEnumerator];
	
	while(i=[en nextObject])
	{
		[anInv invokeWithTarget:i];
	}
}

@interface NSArray (Trampolines)
- (id)do;
@end

@implementation NSArray (Trampolines)
- (id)do
{
	return [[[CollectionTrampoline alloc] initOnCollection:self] autorelease];
}
@end

[[anArray do] doSomething];
@protocol DOExampleProtocol
-(NSNumber *)myPid;
@end
#import <Cocoa/Cocoa.h>
#import "DOprotocol.h"
#import <sys/types.h>
#import <unistd.h>

@interface VendedObject : NSObject <DOExampleProtocol>{
}
-(NSNumber *)myPid;
@end

@implementation VendedObject
-(NSNumber *)myPid
{
	NSLog(@"Vending out my pid...");
	return [NSNumber numberWithInt:getpid()];
}
@end

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	VendedObject *vo=[[VendedObject alloc] init];

        //get the default DO connection
	NSConnection *conn=[NSConnection defaultConnection];
	BOOL status;

        //set which object we vend, and register with the name server	
	[conn setRootObject:vo];
	status=[conn registerName:@"VendingServer"];
	if(status==NO)
	{
		NSLog(@"Couldn't register as VendingServer");
		exit(EXIT_FAILURE);
	}

        //now wait for connections
	[[NSRunLoop currentRunLoop] run];
	
    [pool release];
    return 0;
}

#import <Foundation/Foundation.h>
#import <stdlib.h>
#import "DOprotocol.h"

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	
	//specify a protocol below for compiler type checking
	id <DOExampleProtocol> clientObject;
	NSNumber *serverPid;
	
	/*find a server with the appropriate name and get a proxy from it.
	 * using nil as the host means localhost-only.
	 */
	clientObject=(id <DOExampleProtocol>)[NSConnection rootProxyForConnectionWithRegisteredName:@"VendingServer" host:nil];
	/* -setProtocolForProxy: tells the DO mechanism that the remote object
	 * conforms to the specified protocol.  This means that it doesn't check
	 * messages in that protocol before sending them.  Other messages not in
	 * the given protocol may still be sent.
	 */
	[clientObject setProtocolForProxy:@protocol(DOExampleProtocol)];
	
	if(clientObject==nil)
	{
		NSLog(@"Error: did not get a proxy object for VendingServer service");
		exit(EXIT_FAILURE);
	}
	serverPid=[clientObject myPid];
	
	if(serverPid!=nil)
	{
		NSLog(@"Remote server on pid %@",serverPid);
	}
	else
	{
		NSLog(@"Error, did not get the server's pid");
		exit(EXIT_FAILURE);
	}
    [pool release];
    return 0;
}

[myObject valueForKeyPath:@"someVariable"];
[myObject setValue:@"Hello" forKeyPath:@"someVariable"];
[myObject addObserver:myOtherObject forKeyPath:@"someVariable" options:NSKeyValueObservingOptionNew context:NULL];
cd
shared_obj
cd
shared_obj/ix86/mingw32/gnu-gnu-gnu

The comp.lang.objective-C FAQ listing

DOprotocol.h

DOserver.m

DOclient.m

`DOprotocol.h`

`DOserver.m`