单例，NSTimer

单例：
#import "Teacher.h"
static id teacher1=nil;
@implementation Teacher
+(id)getInstance{//这里的id最好用Teacher *;
if (teacher1==nil) {
teacher1=[[self alloc]init];
}
return teacher1;
}
@end

全的单例

static ClassA *chassA=nil;

+(ClassA *)getClassA{

if(classA==nil){

classA=[[super allocWithZone:NULL]init];

}

return classA;

}

 

+(id)allocWithZone:(NSZone *)zone{

return [[self getClassA]retain];

}
-(id)copy{

return self;

}

-(id)retain{

return self;

}

-(NSUInteger)retainCount{

return NSUIntegerMax;

 

}

-(void)release{

//不做任何处理。

}

-(void)autorelease{

return self;

}

NSTimer:
#import "Dog.h"

@implementation Dog
@synthesize ID;
int i=3;
-(id)init{

self=[super init];
if (self) {
timer=[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(showTimer:) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];

while (i>0) {
[[NSRunLoop currentRunLoop]runUntilDate:[NSDate dateWithTimeIntervalSinceNow:1.0f]];
i--;
}

}
return self;
}
-(void)showTimer:(id)arg{
darkCount++;
NSLog(@"dog %d is calling %d",ID,darkCount);


}
@end