IOS ——OC——浅谈自定义初始化方法-便利构造器的使用

便利构造器的概念:
  • 便利构造器是一种快速创建对象的方式。
  • 它本质上是把初始化方法做了一次封装,方便外界使用。
  • 便利构造器是一个类方法。
  • 通常以类名开头,返回值仍然是id类型。       
在初始化的同时给成员变量赋值
初始化,产生一个对象,将其赋值给实例变量(对象)

注: 

  • 便利构造器的命名规范:必须以类名开头。
  • person的便利构造器为:[[[Person alloc]  init]  autorelease];   

       [[Person alloc] initWithAge:age andWithName:name];//有两个属性的写法,
 
便利初始化的调用:
 Person *p  = [Person initWithAge: 10 andWithName: @"jason"];// 在init时就赋值了age和name属性
 
便利初始化方法声明:
-(类名 *)initWith成员变量名:(类型)参数名
实现部分:
- (Student *)initWithName:(NSString *)newName{
    self = [super init];//通过父类调用init初始化方法,产生一个对象,此处的self就是类的对象 
    //判断是否初始化成功,未初始化之前,self = nil
    if (self) {
        //如果初始化成功,则进行相关操作(比如,给成员变量赋值)
        name = newName;
    }
    //将初始化完成后的对象返回
    return self;
}
 
便利构造器方法声明:
+(类名 *)类名小写With变量名
+ (Student *)studentWithName:(NSString *)newName andAge:(int)newAge;
便利构造器实现:
+(Student *)studentWithName:(NSString *)newName andAge:(int)newAge{
   
   //初始化一个对象
 
//原始的初始化方法
    Student *stu = [[Student alloc] init];
    //给成员变量赋值(类方法里无法直接使用成员变量,因为成员变量属于对象)
    stu->name = newName;
    stu->age = newAge;

   
   //便利初始化
   // Student *stu = [[Student alloc] initWithName:newName andAge:newAge];
    NSLog(@"---%@",stu->name);
    //将初始化完成后的对象返回
    return stu;
}
 便利构造器的调用,
  [类名  方法名 ];
  Student *stu = [Student studentWithName:@"老三" andAge:20];
例:
类接口:
#import
@interface Car : NSObject
{
    NSString *mark;
    NSString *color;
    float    price;
    int      seat;
}
-(Car*)initWithMark:(NSString*)newMark andColor:(NSString*)newColor andPrice:(float)newPrice  andSeat:(int)newSeat;
-(void)introduction;
@end
类实现:
#import "Car.h"
@implementation Car
-(Car*)initWithMark:(NSString *)newMark andColor:(NSString *)newColor andPrice:(float)newPrice andSeat:(int)newSeat
{
    self = [super init];
    if (self) {
        mark = newMark;
        color = newColor;
        price = newPrice;
        seat = newSeat;
    }
    return self;
}
-(void)introduction
{
    NSLog(@"我是一辆%@汽车我是%@颜色我的售价是%.2f我有%d个座位!",mark,color,price,seat);
}
@end
主程序:
#import
#import "Car.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Car *car = [[Car alloc]initWithMark:@"Audi"  andColor:@"yellow"andPrice:100000000 andSeat:7];
       
    [car introduction];
    }
    return 0;
}
运行结果:
2015-10-20 15:33:07.707 10.20 下午课堂练习[2177:100206] 我是一辆Audi汽车我是yellow颜色我的售价是100000000.00我有7个座位!
运用便利构造器的例子:
(1)
类接口:
#import
@interface AudiCar : NSObject
{
    NSString *color;
    float price;
    int seat;
}
-(AudiCar*)initWithColor:(NSString*)newcolor andPrice:(float)newprice andSeat:(int)newseat;
+(AudiCar*)audiCarWithColor:(NSString*)newcolor andPrice:(float)newprice andSeat:(int)newseat;
-(void)introduction;
@end
类实现:
#import "AudiCar.h"
@implementation AudiCar
-(AudiCar *)initWithColor:(NSString *)newcolor andPrice:(float)newprice andSeat:(int)newseat
{
    self = [super init];
    if(self)
    {
        color = newcolor;
        price = newprice;
        seat = newseat;
    }
    return self;
}
+(AudiCar *)audiCarWithColor:(NSString *)newcolor andPrice:(float)newprice andSeat:(int)newseat
{
    AudiCar *car = [[AudiCar alloc]initWithColor:newcolor andPrice:newprice andSeat:newseat];
     return car;
}
-(void)introduction
{
    NSLog(@"我是%@颜色价格是%f有%d个座位!",color,price,seat);
}
@end
主程序:
#import
#import"AudiCar.h"
int main(int argc, const char * argv[])
{
    @autoreleasepool
   {
    AudiCar *car = [AudiCar audiCarWithColor:@"yellow" andPrice:41000.3 andSeat:7];
        [car introduction];
     }
    return 0;
}
运行结果:
2015-10-20 17:48:46.997 10.20 便利构造器 [3097:139957] 我是 yellow 颜色价格是 41000.300781 7 个座位!
(2)
类接口:
#import
@interface Teacher : NSObject
{
    NSString *name;
    NSString *sex;
    int age;
    NSString *marriage;
}
-(void)sayHi;
-(void)gotowork;
-(Teacher*)initWithName:(NSString*)newname andSex:(NSString*)newsex andAge:(int)newage andMarriage:(NSString*)newmarriage;
+(Teacher*)teacherWithName:(NSString*)newname andSex:(NSString*)newsex andAge:(int)newage andMarriage:(NSString*)newmarriage;
@end
类实现:
#import "Teacher.h"
@implementation Teacher
-(void)sayHi
{
    NSLog(@"Goodmorning!");
}
-(void)gotowork
{
    NSLog(@"我坐公交车去上班!");
}
-(Teacher*)initWithName:(NSString *)newname andSex:(NSString *)newsex andAge:(int)newage andMarriage:(NSString *)newmarriage
{
    self = [super init];
    if(self)
    {
        name = newname;
        sex = newsex;
        age = newage;
        marriage = newmarriage;
    }
    return self;
}
+(Teacher*)teacherWithName:(NSString *)newname andSex:(NSString *)newsex andAge:(int)newage andMarriage:(NSString *)newmarriage
{
    Teacher *tea = [[Teacher alloc]initWithName:newname andSex:newsex andAge:newage andMarriage:newmarriage];
    return tea;
}
-(NSString*)description
{
    return[NSString stringWithFormat:@"我叫%@是个%@性今年%d目前%@!",name,sex,age,marriage];
}
@end
主程序:
#import
#import "Teacher.h"
int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        Teacher *tea = [Teacher teacherWithName:@"xxx" andSex:@"男"andAge:28 andMarriage:@"未婚"];
        [tea sayHi];
        [tea gotowork];
         NSLog(@"%@",tea);
    }
    return 0;
}
运行结果:
2015-10-20 21:15:29.776 assignment  1[4336:196173] Goodmorning!
2015-10-20 21:15:29.777 assignment  1[4336:196173]
我坐公交车去上班!
2015-10-20 21:15:29.777 assignment  1[4336:196173] 我叫xxx是个男性今年28目前未婚
 

转载于:https://www.cnblogs.com/Rong-Shengcom/p/4939942.html

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