Objective C : Given a Class id, can I check if this class implements a certain protocol? Or has a certain selector?
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23-09-2019 - |
문제
I want to use this for an object factory: Given a string, create a Class, and if this Class supports a protocol (with a Create() method) then alloc the class and call Create.
해결책
Class klass = NSClassFromString(classname);
if ([klass instancesRespondToSelector:@selector(create)]) {
[[klass alloc] create];
}
May I, however, point out just how many awful Objective-C rules you're breaking by doing the above? For example, you should never be calling methods on an allocated-but-not-initialized instance. The Xcode Static Analyzer will give you all sorts of warnings about memory leaks.
A better option would be this:
[[[klass alloc] init] create];
But you seem to imply that you don't want to call init.
You could consider a class method: [klass create]
, which would return a non-owned instance of klass
. Then you'd just check [klass respondsToSelector:@selector(create)]
before calling it.
다른 팁
NSString *className; //assume this exists
Class class = NSClassFromString(className);
if ([class conformsToProtocol:@protocol(SomeProtocol)]) {
id instance = [[class alloc] init];
[instance create];
}
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