关于ios：“@private”在Objective-C中意味着什么？

What does “@private” mean in Objective-C?

在目标C中，@private是什么意思？

正如HTW所说，它是一个可见性修改器。@private表示只能从同一类的实例中直接访问ivar(实例变量)。然而，这对你来说可能并不重要，所以让我举个例子。为了简单起见，我们将使用类的init方法作为示例。我将在线评论，指出感兴趣的项目。

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@interface MyFirstClass : NSObject
{
@public
int publicNumber;

@protected // Protected is the default
char protectedLetter;

@private
BOOL privateBool;
}
@end

@implementation MyFirstClass
- (id)init {
if (self = [super init]) {
publicNumber = 3;
protectedLetter = 'Q';
privateBool = NO;
}
return self;
}
@end

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@interface MySecondClass : MyFirstClass // Note the inheritance
{
@private
double secondClassCitizen;
}
@end

@implementation MySecondClass
- (id)init {
if (self = [super init]) {
// We can access publicNumber because it's public;
// ANYONE can access it.
publicNumber = 5;

// We can access protectedLetter because it's protected
// and it is declared by a superclass; @protected variables
// are available to subclasses.
protectedLetter = 'z';

// We can't access privateBool because it's private;
// only methods of the class that declared privateBool
// can use it
privateBool = NO; // COMPILER ERROR HERE

// We can access secondClassCitizen directly because we
// declared it; even though it's private, we can get it.
secondClassCitizen = 5.2;
}
return self;
}

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@interface SomeOtherClass : NSObject
{
MySecondClass *other;
}
@end

@implementation SomeOtherClass
- (id)init {
if (self = [super init]) {
other = [[MySecondClass alloc] init];

// Neither MyFirstClass nor MySecondClass provided any
// accessor methods, so if we're going to access any ivars
// we'll have to do it directly, like this:
other->publicNumber = 42;

// If we try to use direct access on any other ivars,
// the compiler won't let us
other->protectedLetter = 'M'; // COMPILER ERROR HERE
other->privateBool = YES; // COMPILER ERROR HERE
other->secondClassCitizen = 1.2; // COMPILER ERROR HERE
}
return self;
}

所以为了回答您的问题，@private保护ivars不被任何其他类的实例访问。注意，myfirstclass的两个实例可以直接访问彼此的所有ivar；假设程序员直接完全控制了这个类，他将明智地使用这个能力。