Objective C object by string name?

问题:

Is it possible to find the object named with specific string.

For example i can use that in php

$objectname="foo";
$foo="bar";
echo $$objectname="bar";

is this possible? objectbyname would a proper function for this.

回答1:

It could be possible if you stored named objects as properties or in some sort of dictionary. Then you could do something like this:

// Put object into dictionary
[dictionaryWithObjects setValue:someNamedObject forKey:@"someNamedObject"];

// and then retrieve it
id object = [dictionaryWithObjects valueForKey:@"someNamedObject"];

And I'm not sure ObjectiveC supports that level of metaprogramming.

回答2:

It doesn't look quite as it does in PHP but, yes, it is possible to get a class from a string. You use the NSClassFromString function.

For example the following two lines are equivalent:

id a = [[NSClassFromString(@"NSString") alloc] init];
id a = [[NSString alloc] init];

回答3:

You can use NSClassFromString() to get a class, but for specific instances of an object I don't think this is possible.