“可变未声明”编译到iOS设备时出错，而不是模拟器 [英] "Variable Undeclared" error when compiling to iOS Device, but not for Simulator

问题描述

我有一个自定义UIVIewController，它是其他控制器的基类，并有一个自定义UIView变量的实例，可通过继承这些类访问。

BaseViewController。 h

  @interface BaseViewController：UIViewController {
 UIView * _vwHeader; 
} 
 
 @end 
  

BaseViewController.m

  #importBaseViewController.h
 @implementation BaseViewController 
 
  - （void）loadView {
 
 [super loadView]; 
 
 _vwHeader = [[UIView alloc] init]; 
} 
 
 @end 
  

CustomViewController.h

  #importBaseViewController.h
 @interface CustomViewController：BaseViewController 
 
 @end 
  

CustomViewController.m

  #importCustomViewController.h
 @implementation CustomViewController 
 
  - （void）loadView 
 {
 [super loadView]; 
 
 [_vwHeader setHidden：NO]; 
} 
 
 @end 
  

问题是，当我我在模拟器上运行它的一切工作完美，但是当我改变到设备我有一个错误在 [_ vwHeader setHidden：NO]; 行说：'_ vwHeader'undeclared（在此函数中第一次使用）

我已经尝试过：

• 注释这行代码，但是它给我一个错误在另一个类使用基类的变量，同样的方式（它只返回一个错误），所以看起来它不是视图或控制器类中的具体错误，因为错误发生在具有不同类型的其他clases中，例如 UIView 和 NSObject types


• 更改目标编译器配置，如：architectures（所有），base sdk

似乎可以解决问题，但不完全

• 为 _vwHeader 创建属性并通过 self._vwHeader 或 super._vwHeader 似乎工作，但是必须创建一个属性只是为了访问一个变量不让我confortable，特别是因为我必须为我的项目中的同一种情况下的所有变量。


• 更改了C / C ++编译器版本：使用 Apple LLVM Compiler 2.1 使编译错误消失，与项目中使用的其他库有关的其他问题。因此，它不是一个确定的解决方案，但可能是一个线索的问题是什么。

/ p>

我试图创建另一个不是指针的变量， BOOL 而不是 UIView * ，然后在继承的类中使用它：

EDIT（2）：

我没有任何属性在任何我的类，我仍然得到的错误。
我只是添加了测试porpouses的属性，看看父类中的属性是否导致相同的行为，显然它不是。
这也是奇怪的是，当我得到错误的变量，我检查了我的intellisense，它找到... ...

解决方案

为了引用 self 以外的任何对象中的实例变量，包括 super ，必须使用结构指针运算符（ - > ）。实例变量的默认范围是protected，这意味着它只能在它定义的类中或该类的子类中访问。因为 CustomViewController 是 BaseViewController 的子类，所以这个范围足以使用 self - > _vwHeader ，但如果你试图从这里做的第二个类不是一个子类，你还需要改变范围为 @public 或 @package 。

总之，将您的方法调用更改为：

  [self-> _vwHeader setHidden：NO]; 
  

，它应该适用于基本视图控制器的任何子类。

I have an custom UIVIewController that is the base class for other controllers and has an instance of a custom UIView variable that is accessed by inherited the classes.

BaseViewController.h

@interface BaseViewController : UIViewController {
    UIView *_vwHeader;
}

@end

BaseViewController.m

#import "BaseViewController.h"
@implementation BaseViewController

-(void)loadView {

    [super loadView];

    _vwHeader = [[UIView alloc] init];
}

@end

CustomViewController.h

#import "BaseViewController.h"
@interface CustomViewController : BaseViewController

@end

CustomViewController.m

#import "CustomViewController.h"
@implementation CustomViewController

- (void)loadView
{
    [super loadView];

    [_vwHeader setHidden:NO];
}

@end

The problem is that when I am running it on the simulator everything works perfectly fine, but when I change to the device I have an error on the [_vwHeader setHidden:NO]; line which says: '_vwHeader' undeclared (first use in this function)

I already tried to do:

• Comment this line of code, but then it gives me an error in another class using a variable from the base class the same way (It only returns one error at a time), so it seems that it is not an specific error in the view or the controller class as the error occurs in other clases with different types, such as UIView and NSObject types
• Change target compiler configuration, such as: architectures (all of them), base sdk (all above 4.0) didn't change anything

What seem to solve the problem, but not completely

• Creating a property for _vwHeader and accessing it by self._vwHeader or super._vwHeader seems to work, but having to create a property just to access a variable does not make me confortable, specially because I would have to do it for all variables in the same situation inside my project.
• changed C/C++ compiler version: using Apple LLVM Compiler 2.1 makes the compilation error goes away, but gives a bunch of other problems with other libraries being used in the project. So, it is not a definitive solution, but might be a clue of what the problem is.

EDIT:

I tried to create another variable that is not a pointer, a BOOL instead of the UIView * and then used it in the inherited class: the problem also occurs

EDIT (2):

I have no properties whatsoever in any of my classes and I still get the error. I just added the properties for test porpouses, to see if a property in a parent class caused the same behaviour, and apparently it doesn't. Something that is also weird is that when I get the error in the variable, I checked with my intellisense and it finds it...

解决方案

In order to refer to an instance variable within any object other than self, including super, you must use the structure pointer operator (->). The default scope of an instance variable is protected, which means it can only be accessed within the class it is defined in or a subclass of that class. Since CustomViewController is a subclass of BaseViewController, this scope is sufficient to access the variable using self->_vwHeader, but if the second class you were trying to do this from is not a subclass you will also need to change the scope to either @public or @package.

In summary, change your method call to:

[self->_vwHeader setHidden:NO];

and it should work for any subclasses of the base view controller.

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