objective-c如何实现java中的反射机制

Question

在开发iOS app时，经常会遇到服务端返回数据不完整的情况，比如缺少key，或者value为null的情况。

java中可以定义一个类，用反射的机制来进行数据初始化。

而objective-c中只能用nil和[NSNull null]来单独判断。来避免app crash。

整个view层也变得不够纯粹。

补充:
我现在的做法是。如果返回的是一个数组。数组中每一项又是一个对象。我们假设对象中有的key或者value是缺失的。那么就要遍历一边，逐个遇到不完整的情况追加key或者默认值。这样，在view层中，就不用再对key或value去做判断了。代码也专注在业务逻辑上。

问：
有没有更好的。更优雅的方式来实现。

Answer 1

I don’t quite understand what you mean. . . Java's reflection can dynamically obtain the method and attribute list of an instance. For this function, Obj-c can use NSObject's respondsToSelector: method to confirm whether an instance has a certain method; it can also use performSelector: to call the method. . Basically it can replace Java's reflection.
As for the problem of judging empty return value, I really don’t have a good way at the moment. I usually define a method and judge containsObject:, nil, [NSNull null], length or count in sequence. This method can be written in a util or can be extended and written in NSDictionary and NSArray.

Answer 2

objc’s KVC mechanism is similar to java’s reflection. Please google it

For example
@interface A : NSObject{
NSString * name;
}

You can get it like this

A *a = [[A alloc] init];

NSString *name = [a objectForKey:@"name"];

I don’t know if you want this

You implement the nscoding interface. - (id)initWithCoder:(NSCoder *)aDecoder can do what you want. I don't know if I understand it correctly.

Answer 3

• OC has an open source framework of JSONModel, which can convert Json into ViewModel

• The problem of null value can be determined when the View layer is used or the default value can be set when the ViewModel is constructed

• Regarding reflection of OC, you can use NSClassFromString, NSSelectorFromString and other methods