LHF Objective-C语法（4）对象初始化

1、Fraction *frac = [[Fraction alloc]  init];

    [Fraction alloc]  分配内存，并赋初值 ，返回对象的指针

    init 是在创建对象中可以参与的方法

#import <Foundation/Foundation.h>static int t= 0;@interface Fraction : NSObject{ int numerator; //分子 @public int denominator; //分母}-(id) init;-(Fraction*) initWithNumerator:(int) numerator andDenominator:(int) denominator;-(void) setNumerator:(int) numerator;-(void) setDenominator:(int) denominator;-(void) setNumerator:(int) numerator andDenominator:(int) denominator;-(int) numerator;-(int) denominator;-(void) print;+(void) t;@end增加了2个方法init  initWithNumerator

#import "Fraction.h"@implementation Fraction-(id) init{ self = [super init];}-(Fraction*) initWithNumerator:(int) n andDenominator:(int) d{ self = [self init]; if(self){ [self setNumerator:n andDenominator:d]; } return self;}-(void) setNumerator:(int) n{ numerator = n;}-(void) setDenominator:(int) d{ denominator = d;}-(void) setNumerator:(int) n andDenominator:(int) d{ numerator = n; denominator = d;}-(int) numerator{ return numerator;}-(int) denominator{ return denominator;}-(void) print{ NSLog(@"%d/%d",numeraotr,denominator);}-(void) m{ NSLog(@"-m:The class varable t is %d",++t);}+(void) t{ NSLog(@"+t:The class varable t is %d",++t);}@end1、self=[super init] //覆盖了NSObject中的init方法，返回值付给self，让self指向父类init方法返回的对象，

2、self = [self init]; //因为ObjC是动态语言，所以init方法可能返回一个不是当前类行的返回值，

3、if(self) 与 if(self!=nil)是相同的  

int main(int argc,const char * argv[]){ //Fraction *frac = [[Fraction alloc] init]; Fraction *frac = [[Fraction alloc] initWithNumerator:2 andDenominator:3]; //[frac setNumerator:3 andDenominator:5]; [frac print]; NSLog(@"The denominator of Fration is %d\n",frac->denominator); [Fraction t]; [frac m]; [frac release]; return 0;}
1、main方法里就可以用新的初始化方法了