如何使用@encode()获取@“NSArray” 在 Objective-C 中
我正在使用运行时函数来获取属性的类型（感谢 eJames 帮助我找出这种方法）。 属性的属性字符串如下所示：
T@"NSArray",&,Vstuff
我需要检查属性类型是否是数组，目前我正在这样做：
- (BOOL)valueForKeyIsArray:(NSString *)key fromTagret:(id)target
{
NSString *lowerCaseKey = [self convertToKVCKey:key];
objc_property_t property = class_getProperty([target class], [lowerCaseKey UTF8String]);
NSString *propertyAttrs = [NSString stringWithUTF8String:property_getAttributes(property)];
NSString *encodedType = @"@\"NSArray\"";
NSRange range = [propertyAttrs rangeOfString:encodedType options:NSLiteralSearch];
return range.location != NSNotFound;
}
但是由于Apple可以随时更改类型定义字符串，我想生成这个@“NSArray”类型的字符串。 我用@encode()尝试过，但是没有用：
NSString *encodedType = [NSString stringWithUTF8String:@encode(NSArray *)];
那么如何生成这种类型的字符串呢？ 或者是否有更好的方法来检查此属性属性是否包含数组类型？
I'm using the runtime functions to get the type of a property (thanks to eJames for helping me to figure out this way).
The attribute string of the property looks like this:
T@"NSArray",&,Vstuff
I need to check if the property type is an array, at the moment I'm doing it like this:
- (BOOL)valueForKeyIsArray:(NSString *)key fromTagret:(id)target
{
NSString *lowerCaseKey = [self convertToKVCKey:key];
objc_property_t property = class_getProperty([target class], [lowerCaseKey UTF8String]);
NSString *propertyAttrs = [NSString stringWithUTF8String:property_getAttributes(property)];
NSString *encodedType = @"@\"NSArray\"";
NSRange range = [propertyAttrs rangeOfString:encodedType options:NSLiteralSearch];
return range.location != NSNotFound;
}
But since Apple can change the type definition string at any time, I would like to generate this @"NSArray" type string. I tried it with @encode(), but it did not work:
NSString *encodedType = [NSString stringWithUTF8String:@encode(NSArray *)];
So how can I generate this type string? Or is there a better way to check if this property attributes contain the array type?
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没有办法检查这一点。 在 Objective-C 源代码中，类型为 NSArray * 的变量仅用于编译器发出警告。 它没有任何意义，并且在运行时不存在。 如果您将
NSArray错误地输入为NSString，编译时您会收到很多警告，但您的代码在运行时的行为完全相同。 在运行时，我们知道 ivar/property 是“一个对象”。另一种思考方式是，一旦 Objective-C 被编译，所有对象引用都是 id 引用。
There is no way to check this. In Objective-C source code the variables being typed as
NSArray *is only there for the compiler to issue warnings. It has no meaning, and does not exist at runtime. If you mis-typed anNSArrayas anNSString, you would get lots of warnings when compiling, but your code would behave exactly the same when run. At runtime all that is known is that the ivar/property is "an object".Another way to think of it, is that once Objective-C is compiled, all object references are
idreferences.只要接受这样一个事实：如果运行时发生变化，您的代码将会崩溃，然后继续前进。 但是，我认为您可能对
NSMutableArray *、CFArrayRef或CFMutableArrayRef类型的 ivars 进行了错误分类。 您似乎还假设所有键都直接对应于声明的属性。最干净的解决方案可能是断言用于测试的示例对象（目标）必须具有该键的非零值，并且只需获取该值并测试
[[target valueForKey:key] isKindOfClass :[NSArray 类]]。Just accept that if the runtime changes, your code will break, and move on. However, I think you might be miscategorizing ivars of type
NSMutableArray *,CFArrayRef, orCFMutableArrayRef. You also seem to be assuming all keys correspond directly to a declared property.The cleanest solution might be to assert that the sample object being used for the test (the target) must have a non-nil value for that key, and just grab the value and test that
[[target valueForKey:key] isKindOfClass:[NSArray class]].