多態(tài)：同一種類型 具有多種的表現(xiàn)形態(tài)
多態(tài)的條件：
必須存在繼承關(guān)系
子類重寫父類的方法
??父類聲明的變量指向子類對象
（父類聲明子類對象）
創(chuàng)建父類：Printer
創(chuàng)建子類：BlackPrinter 、ColorPrinter 、 OtherPrinter 繼承Printer
Printer.h
#import <Foundation/Foundation.h>
@interface Printer : NSObject
- (void)print;
- (void)doPrint:(Printer *)printer;
@end
Printer.m
#import "Printer.h"
@implementation Printer
//使用打印機
- (void)doPrint :(Printer *)printer
{
[printer print];
}
- (void)print
{
NSLog(@"打印機 打印...");
}
@end
BlackPrinter.m
#import "BlackPrinter.h"
@implementation BlackPrinter
- (void)print
{
NSLog(@"黑白打印機 打印黑白效果");
}
@end
ColorPrinter.m
#import "ColorPrinter.h"
@implementation ColorPrinter
- (void)print
{
NSLog(@"彩色打印機");
}
@end
OtherPrinter.m
#import "OtherPrinter.h"
@implementation OtherPrinter
- (void)print
{
NSLog(@"其他類型打印機")；
}
@end
main.m
#import <Foundation/Foundation.h>
#import "BlackPrinter.h"
#import"ColorPrinter.h"
#import"Printer.h"
#import"OtherPrinter.h"
int main(int argc, const char *argv[])
{
@autoreleasepool
{
enum KindOfPrinter //枚舉
{
colorPrinter = 1,
blackPrinter,
otherPrinter
}; //分號
enum KindOfPrinter printerKind;
NSLog(@"請選擇打印機:(1彩色 2黑色 3其他)")；
scanf("%d",&printerKind);
//父類聲明變量
Printer *printer;
//根據(jù)類型 選擇初始化方法的過程
if(printerKind == colorPrinter)
{
printer = [[ColorPrinter alloc]init];
}
else if(printerKind == blackPrinter)
{
printer = [[BlackPrinter alloc]init];
}
else if(printerKind == otherPrinter)
{
printer = [[OtherPrinter alloc]init];
}
[printer print];
}
return 0;
}
