自动生成getter和setter方法

作者：追风剑情发布于：2019-2-21 12:15 分类：Objective-C

示例一：利用@property和@synthesize指令自动生成getter和setter

Fraction.h

#import <Foundation/Foundation.h>
 
@interface Fraction : NSObject
 
//@property指令让编译器自动为numerator、denominator生成getter、setter方法
@property int numerator, denominator;
 
-(void) print;
-(double) convertToNum;
 
@end

Fraction.m

#import "Fraction.h"
 
@implementation Fraction
 
//@synthesize与@property指令配合使用来自动生成getter、setter方法
//会自动生成设值方法setNumerator、setDenominator
//会自动生成取值方法numerator、denominator
@synthesize numerator, denominator;
 
-(void) print
{
    NSLog(@"%i/%i", numerator, denominator);
}
 
-(double) convertToNum
{
    if (denominator != 0)
        return (double) numerator / denominator;
    else
        return NAN;
}
 
@end

main.m

#import <Foundation/Foundation.h>
#import "Fraction.h"
 
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Fraction *myFraction = [[Fraction alloc] init];
        
        //[myFraction setNumerator: 1];
        //[myFraction setDenominator: 3];
        //使用点语法设值(即,调用setter方法),与上面两句代码等价
        myFraction.numerator = 1;
        myFraction.denominator = 3;
        
        
        NSLog(@"The numerator is %i, and the denominator is %i",
              myFraction.numerator, myFraction.denominator);
        
        
    }
    return 0;
}

运行测试

示例二：省略@synthesize指令

Fraction.h

#import <Foundation/Foundation.h>
 
@interface Fraction : NSObject
 
//@property指令让编译器自动为numerator、denominator生成getter、setter方法
@property int numerator, denominator;
 
-(void) print;
-(double) convertToNum;
 
@end

Fraction.m

#import "Fraction.h"
 
@implementation Fraction
 
//@synthesize与@property指令配合使用来自动生成getter、setter方法
//会自动生成设值方法setNumerator、setDenominator
//会自动生成取值方法numerator、denominator
//@synthesize numerator, denominator;
 
-(void) print
{
    //如果省略了@synthesize指令,那么实例变量前要加下画线。
    NSLog(@"%i/%i", _numerator, _denominator);
}
 
-(double) convertToNum
{
    //如果省略了@synthesize指令,那么实例变量前要加下画线。
    if (_denominator != 0)
        return (double) _numerator / _denominator;
    else
        return NAN;
}
 
@end

main.m

#import <Foundation/Foundation.h>
#import "Fraction.h"
 
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Fraction *myFraction = [[Fraction alloc] init];
        
        //[myFraction setNumerator: 1];
        //[myFraction setDenominator: 3];
        //使用点语法设值(即,调用setter方法),与上面两句代码等价
        myFraction.numerator = 1;
        myFraction.denominator = 3;
        
        
        NSLog(@"The numerator is %i, and the denominator is %i",
              myFraction.numerator, myFraction.denominator);
        
        
    }
    return 0;
}