问题描述
我正在尝试将非ARC项目转换为使用ARC，但由于某种原因，它抱怨使用所有实例变量.
I am trying to convert non-ARC project to use ARC but for some reason its complaining about the use of all instance variables.
@property (nonatomic,retain)id myvariable;
产生
Error : "Use of undeclared variable _myvariable"
我的代码中有些地方我不想修改保留计数，但要对该属性进行赋值.所以我使用一个实例变量.
there are some places in my code where I don't want to modify retain count but do an assignment to the property. so I use an instance variable.
添加@syhtnesize myvariable =_myvariable可解决此问题，但我试图找出解决此问题的正确方法.
adding @syhtnesize myvariable =_myvariable resolves this problem but I am trying to figure out the right way to fix this.
可能的解决方案:
1)添加synthesize
2)将实例变量的使用替换为self.myvariable，并分配属性.
2) replace use of instance variable with self.myvariable and make property assigned.
问题扩展 ARC错误
推荐答案
这听起来像是您实现了向后兼容性功能.
It sounds like you've hit a backward compatibility feature.
由于Xcode 4.4属性声明不再需要@synthesize语句，并且没有该声明，编译器会自动生成_propertyName实例变量.
Since Xcode 4.4 property declarations no longer require an @synthesize statement and without one the compiler auto-generates an _propertyName instance variable.
但是对于@synthesize propertyName，就像您在Xcode 4.4之前一样，编译器将自动生成propertyName-不带下划线-实例变量.
However with an @synthesize propertyName, as you would pre-Xcode 4.4, then the compiler will auto-generate an propertyName - note no underscore - instance variable.
警告您使用未声明的变量_myvariable"的编译器消息建议您已将代码切换为使用下划线，但仍有一些@synthesize myvariable语句.
The compiler messages warning you "Use of undeclared variable _myvariable" suggest you have switched the code to use underscores but still have some @synthesize myvariable statements.
您使用@synthesize myvariable = _myvariable直接指定用于实例变量的名称，因此可以解决您的问题，但是通常删除@synthesize是常见的方法.
Your use of @synthesize myvariable = _myvariable specifies the name to use for the instance variable directly, and so solves your problem, but removing the @synthesize completely is the usual approach.
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