Objective-C：类作为参数

Question

is it possible to create an object of a type class A, knowing that A was passed as a parameter. Typically:

Class A=[MyClass class];
....
A * object=[[A alloc]...]; //incorrect code here !

Thanks !

Answer 1

You can't use a variable as the type of a variable. You need to use id .

Class A = [MyClass Class];
....
id object = [[A alloc]...];

Answer 2

A is a variable, in fact it is a reference to an object much like all the other objects. You can't therefore use it where the compiler is expecting type. You should declare object as an id or some other superclass of the types you know that A could be. The following code works fine, for example.

-(void) testFooBar
{
    Class foo = [NSMutableString class];
    NSString* bar = [[foo alloc] initWithFormat: @"Message: %@", @"Hello, World"];
    NSLog(@"bar is %@, class name %@", bar, [bar className]);
}

And produces the following

2014-04-17 16:29:49.962 BigNumber[62212:303] bar is Message: Hello, World, class name __NSCFString