oc 01 类、异常处理

类的语法

Fraction.h 类声明

#import <Foundation/Foundation.h>
#ifndef Fraction_h
#define Fraction_h

static int t = 0 ; // 类变量
@interface Fraction:NSObject{
    int numerator;
@public int denominator;
}
-(void)setNumerator:(int)numerator;
-(void)setDenominator:(int)denominator;
-(void)setNumerator:(int)numerator andDenominator:(int)denominator;

-(int)numerator;
-(int)denominator;
-(void)print; // 成员方法
+(void)t;       // 类方法

@end

#endif /* Fraction_h */

Fraction.m 类定义

#import "Fraction.h"
#import "ZeroException.h"

@implementation Fraction

-(void)setNumerator:(int)n{
    numerator = n;
}
-(void)setDenominator:(int)d{
    if(d==0){
        NSException *e = [ZeroException exceptionWithName:@"ZeroException" reason:@"denominator cant be 0!" userInfo:nil];
        @throw e; // 抛出异常
    }
    denominator = d;
}
-(void)setNumerator:(int)n andDenominator:(int)d{
    if(d==0){
        NSException *e = [ZeroException exceptionWithName:@"ZeroException" reason:@"denominator cant be 0!" userInfo:nil];
        @throw e;
    }
    numerator  = n;
    denominator = d;
}
-(int)numerator{
    return numerator;
}
-(int)denominator{
    return denominator;
}
-(void)print{
    printf("%d/%d\n",numerator,denominator);
}
+(void)t{
    printf("+t:thie class variable t is %d\n",++t);
}
-(NSString*)description{  // toString
    return @"I am a fraction";
}

@end

ZeroException.h 异常声明

#import <Foundation/Foundation.h>

@interface ZeroException:NSException
@end

ZeroException.m 异常定义

#import <Foundation/Foundation.h>
#import "ZeroException.h"

@implementation ZeroException

@end

main.c

#import <Foundation/Foundation.h>
#import "Fraction.h"
#import "ZeroException.h"

int main(int argc , const char* argv[])
{
    Fraction *frac = [[Fraction alloc]init];
    [frac setNumerator:3 andDenominator:4];
    [frac print];
    [Fraction t];
    NSLog(@"%@",frac); // description方法
    
    @try{
        [frac setDenominator:0];
    }@catch(ZeroException *ze){ // 捕获异常
        printf("%s\n",[[ze reason] cString]);
    }@finally{
        printf("finally run");
    }
    return 0 ;
}