Question

在接口中申报变量时,两者之间的差别是:

@interface thing:NSObject {
    int x;
    int y;
}
@property int x, y;

:

@interface thing:NSObject {
    @public
    int x;
    int y;
}

Answer 1

@public is an access modifier that means You can access an identity direct such as this:

obj->someAttrib;

@property表示,汇编者应当创造出入口方法(如果你重新使用@synthesize)。

重要的是,财产不一定与归属相称。你们能够创造这样的美好环境:

@property(readonly) int doSmth;

之后执行:

-(int) doSmth {
   return 123+456;
}

然而,这是非常粗略和不完整的解释(在财产方面尤其如此)。阅读一些关于ObjC的文章/书籍。

Answer 2

财产申报和对应的@synthesize声明将为标明的x和 y.公开宣布贵方变量的数值设定标准入口,将使贵方的编码能够直接查阅贵方的储存价值。

Answer 3

default is @protected so the only difference is if you wanted to access them directly, which is generally considered bad practice, but in the first example you could not do:

thing * aThing = [[thing alloc] init];
aThing->x = 5;

Edit: (as I got voted down by answering the actual question not the implied question.)

In Objective-C there are 3 visibility specifiers: @public; @private; and @protected.

The syntax only affects visibility of iVars, not methods, all methods are publicly visible.

the specifier works for all iVars following until it reaches another specifier;

@public allows direct access of ivars from outside of instances of the class or subclass.

@protected allows direct access of ivars from only in instances of the class or subclasses thereof.

允许在班级内直接使用批量,但不得分级。

as for @property it is a language construct introduced with Objective-C 2.0 that allows you to use the . (dot) accessor for calling methods.

the default behavior is @property int x will reference 2 methods depending if you are using it as an left hand(setter) or right hand(getter) operator, the default getter will be -(int)x; and the default setter will be -(void)setX:(int)x;, @property doesn t in itself create those methods, but allows access to them.

the default behavior can be overridden with the following syntax @property(getter=somethingOtherThanX,setter=somethingOtherThanSetX:)int x;

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