宏定义 #define

 定义形式 #define 标识符 字符串

含参数的 #define a(b) 2*b; 

当需要参数拼接时 用##   #define FunctionTest(a)  -(void)te##a{NSLog(@"test");} 

需要换行时  用\ #define str(a,b,c) {a+=b;a+=c;}

 #define str(a,b,c) {a+=b;\

　　a+=c;}  

//
//  SynthesizeSingleton.h
//  CocoaWithLove
//
//  Created by Matt Gallagher on 20/10/08.
//  Copyright 2009 Matt Gallagher. All rights reserved.
//
//  Permission is given to use this source code file without charge in any
//  project, commercial or otherwise, entirely at your risk, with the condition
//  that any redistribution (in part or whole) of source code must retain
//  this copyright and permission notice. Attribution in compiled projects is
//  appreciated but not required.
//

#define SYNTHESIZE_SINGLETON_FOR_CLASS(classname) \
 \
static classname *shared##classname = nil; \
 \
+ (classname *)shared##classname \
{ \
    @synchronized(self) \
    { \
        if (shared##classname == nil) \
        { \
            shared##classname = [[self alloc] init]; \
        } \
    } \
     \
    return shared##classname; \
} \
 \
+ (id)allocWithZone:(NSZone *)zone \
{ \
    @synchronized(self) \
    { \
        if (shared##classname == nil) \
        { \
            shared##classname = [super allocWithZone:zone]; \
            return shared##classname; \
        } \
    } \
     \
    return nil; \
} \
 \
- (id)copyWithZone:(NSZone *)zone \
{ \
    return self; \
} \
 \