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Difference between Category and Class Extension?可能重复:类别和类扩展之间的区别?
I am often told that when you want to declare a variable as private you would make a nameless category on the .m file.
我经常被告知，当您想将一个变量声明为private时，您将在.m文件中创建一个无名类别。
Is there anything inherently different in the nameless category as opposed to named categories?
在无名类别中有什么本质上的不同而不是命名类别?
What's the difference?
有什么区别呢?
1 个解决方案
#1
6
What you refer to as a 'nameless category' is called a 'class extension'.
你所说的“无名类”被称为“类扩展”。
One difference is that the compiler expects that declarations in the class extension are defined in the class' @implementation block. That is, you do not declare the extension's @implementation block explicitly when it is in the same translation as the primary @implementation block. They are merged for your convenience. Consequently, the compiler may produce warnings.
一个不同之处是，编译器期望类扩展中的声明是在类' @implementation块中定义的。也就是说，当扩展的@implementation块与主@implementation块处于相同的转换时，不要显式地声明它的@implementation块。为了您的方便，它们被合并了。因此，编译器可能会产生警告。
Another difference is that an extension may declare properties which are synthesized (and consequently resize the type), where a regular category cannot. In addition to properties, instance variables may be declared in the class extension's @interface.
另一个不同之处在于，扩展可以声明被合成的属性(从而调整类型的大小)，而常规类别不能。除了属性之外，实例变量还可以在类扩展的@interface中声明。
Beyond that, it's just convention.
除此之外，这只是惯例。
#1
6
What you refer to as a 'nameless category' is called a 'class extension'.
你所说的“无名类”被称为“类扩展”。
One difference is that the compiler expects that declarations in the class extension are defined in the class' @implementation block. That is, you do not declare the extension's @implementation block explicitly when it is in the same translation as the primary @implementation block. They are merged for your convenience. Consequently, the compiler may produce warnings.
一个不同之处是，编译器期望类扩展中的声明是在类' @implementation块中定义的。也就是说，当扩展的@implementation块与主@implementation块处于相同的转换时，不要显式地声明它的@implementation块。为了您的方便，它们被合并了。因此，编译器可能会产生警告。
Another difference is that an extension may declare properties which are synthesized (and consequently resize the type), where a regular category cannot. In addition to properties, instance variables may be declared in the class extension's @interface.
另一个不同之处在于，扩展可以声明被合成的属性(从而调整类型的大小)，而常规类别不能。除了属性之外，实例变量还可以在类扩展的@interface中声明。
Beyond that, it's just convention.
除此之外，这只是惯例。