目标C:为什么在NSUInteger而不是NSString上无效的接收器类型，却以相同的方式创建

问题描述

我已经为所有字段自动以相同的方式生成了此源代码，为什么编译器会告诉我NSUInteger上的Invalid Receiver类型不是NSString，而是以相同的方式创建:

 /**类代表一个人*/@interface人员:NSObject {//私人成员NSString * _firstName;NSString * _lastName;NSUInteger _age;}//初始化器/**初始化Person类的新实例.@返回一个新初始化的对象*/-(id)initPerson;/**使用初始化Person类的新实例@param firstName名字@param lastName姓氏@param age年龄@返回一个新初始化的对象*/-(id)initPersonWithFirstName:(NSString *)firstName LastName:(NSString *)lastName Age:(NSUInteger)age;//公共访问器-(NSString *)firstName；-(void)setFirstName:(NSString *)input;-(NSString *)lastName;-(void)setLastName:(NSString *)input;-(NSUInteger)年龄；-(void)setAge:(NSUInteger)input;@结尾@实现人//初始化器/**初始化Person类的新实例.@返回一个新初始化的对象*/-(id)initPerson {如果(self = [super init]){}回归自我}/**使用初始化Person类的新实例@param firstName名字@param lastName姓氏@param age年龄@返回一个新初始化的对象*/-(id)initPersonWithFirstName:(NSString *)firstName姓氏:(NSString *)lastName年龄:(NSUInteger)age {如果(self = [super init]){[self setFirstName:firstName];[self setLastName:lastName];[self setAge:age];}回归自我}//公共访问器-(NSString *)firstName {返回_firstName;}-(void)setFirstName:(NSString *)input {[_firstName自动发布];_firstName = [输入保留];}-(NSString *)lastName {返回_lastName;}-(void)setLastName:(NSString *)input {[_lastName自动发布];_lastName = [输入保留];}-(NSUInteger)年龄{返回_age;}-(void)setAge:(NSUInteger)input {[_age自动发布];_age = [输入保留];}@结尾 

解决方案

NSUInteger 是数字类型，而不是对象.您不能向其发送消息，它也不需要内存管理(除非您在堆上 malloc -ing，无论如何这都是一个不同的过程，在这里与此无关)./p>

如果您实际上希望对象类型保存一个数值-您几乎肯定不希望这样-请使用 NSNumber .否则，就像对待 int 或 float 一样对待它.即:

 -(void)setAge:(NSUInteger)input {_age =输入；} 

I have generated this source code automatically the same way for all fields why compiler tells me Invalid Receiver type on NSUInteger and not NSString whereas created the same way:

/**
 class to represent an Person
 */
@interface Person: NSObject {
    // private members
    NSString* _firstName;
    NSString* _lastName;
    NSUInteger _age;
}
// Initializers
/**
 Initializes a new instance of the Person class.
 @returns a newly initialized object
 */
- (id)initPerson;

/**
 Initializes a new instance of the Person class with
 @param firstName The First Name
 @param lastName The Last Name
 @param age The Age
 @returns a newly initialized object
 */
- (id)initPersonWithFirstName:(NSString*)firstName LastName:(NSString*)lastName Age:(NSUInteger)age;

// public accessors
- (NSString*) firstName;
- (void) setFirstName: (NSString*)input;
- (NSString*) lastName;
- (void) setLastName: (NSString*)input;
- (NSUInteger) age;
- (void) setAge: (NSUInteger)input;
@end

@implementation Person
// Initializers
/**
 Initializes a new instance of the Person class.
 @returns a newly initialized object
 */
- (id)initPerson {
    if ( self = [super init] ) {
    }
    return self;
}

/**
 Initializes a new instance of the Person class with
 @param firstName The First Name
 @param lastName The Last Name
 @param age The Age
 @returns a newly initialized object
 */
- (id)initPersonWithFirstName:(NSString*)firstName LastName:(NSString*)lastName Age:(NSUInteger)age {
    if ( self = [super init] ) {
        [self setFirstName:firstName];
        [self setLastName:lastName];
        [self setAge:age];
    }
    return self;
}

// public accessors
- (NSString*) firstName {
    return _firstName;
}
- (void) setFirstName: (NSString*)input {
    [_firstName autorelease];
    _firstName = [input retain];
}
- (NSString*) lastName {
    return _lastName;
}
- (void) setLastName: (NSString*)input {
    [_lastName autorelease];
    _lastName = [input retain];
}
- (NSUInteger) age {
    return _age;
}
- (void) setAge: (NSUInteger)input {
    [_age autorelease];
    _age = [input retain];
}
@end

解决方案

NSUInteger is a numeric type, not an object. You can't send messages to it and it doesn't need memory management (unless you're malloc-ing on the heap, which is a different process anyway and isn't relevant here).

If you actually want an object type to hold a numeric value - which you almost certainly don't - use NSNumber. Otherwise, just treat it as you would an int or float. ie:

- (void) setAge: (NSUInteger)input {
    _age = input;
}

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