ObjectiveC 学习笔记（二） 类继承，组合，多态等

1、 继承的语法如下：

@interface TestCoop : NSObject {
    int iMonth;
    int iYear;
    int iDay;
}

- (void) setYear: (int) iYear;
- (void) primalSetData: (int)iYear :(int)iMonth :(int)iDay;
- (void) setData: (int)Year iMonth:(int)iMonth iDay:(int)iDay;
- (void) displayDateInfo;

@end


@interface TestAddWeather : TestCoop{
    NSString *pstrWeather;
}

- (void) setWeather: (NSString *) pstrWeather;
- (void) displayDateInfo;
@end

@end

2、不过Objective-C不支持多继承，类似如下写法

@interface TestAddWeather : TestCoop, PrintableObect

编译会报错的，不过Objective-C的其他特性可以满足多继承的功能，以后再研究

基本的继承语法和多态也和C++差不多，看实现代码：

@implementation TestCoop
- (void) displayDateInfo{
    NSLog(@"Today is: %d.%d.%d/n", iYear, iMonth, iDay);
}

- (void) setYear: (int) year{
    iYear = year;
}

- (void) primalSetData: (int)year :(int)month :(int)day{
    iYear = year;
    iMonth = month;
    iDay = day;   
}

- (void) setData: (int)year iMonth:(int)month iDay:(int)day{
    iYear = year;
    iMonth = month;
    iDay = day;
}

@end


@implementation TestAddWeather
- (void) setWeather: (NSString *) pWeather{
    [pstrWeather release];
    pstrWeather = nil;
    pstrWeather = [[NSString alloc] initWithString:pWeather];
}
- (void) displayDateInfo{
    NSLog(@"Today is: %d.%d.%d,weather: %@/n", iYear, iMonth, iDay, pstrWeather);
}
@end

测试代码：

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    // insert code here...
    //NSLog(@"%d-,%s %@/n", 12, "hel123lo", @"123");
   
    TestCoop *ptest = [[TestCoop alloc] init];
    [ptest primalSetData :2009 :03 :05];
    [ptest displayDateInfo];
    [ptest setData:2010 iMonth:06 iDay:06];
    [ptest displayDateInfo];
    [ptest setYear:1987];
    [ptest displayDateInfo];
    [ptest release];
    TestAddWeather *ptestweather = [[TestAddWeather alloc] init];
    [ptestweather setData:2010 iMonth:03 iDay:05];
    [ptestweather setWeather:@"Rainy"];
    [ptestweather displayDateInfo];
    [ptestweather setWeather:@"Cloudy"];
    [ptestweather displayDateInfo];
    [ptestweather release];
    [pool drain];
    return 0;
}

打印出如下信息：

Today is: 2009.3.5
Today is: 2010.6.6
Today is: 1987.6.6
Today is: 2010.3.5,weather: Rainy
Today is: 2010.3.5,weather: Cloudy

如果要调用父类的函数，可以在定义函数的时候使用super 关键字

比如：

@implementation TestAddWeather
- (void) setWeather: (NSString *) pWeather{
    [pstrWeather release];
    pstrWeather = nil;
    pstrWeather = [[NSString alloc] initWithString:pWeather];

    [super setYear:2009];
}

3.组合也和C++差不多，而且为了防止头文件重复引用，有和C++一样的用法

当该类成员只通过其他类的指针访问时，可以头文件中不import，只声明

@class TestAddWeather;

如下

然后在.m/.mm文件中import “TestAddWeather.h”,防止头文件依赖关系过多导致编译变慢