Can't access properties of returned objects?

//SomeObject.h
#import <Foundation/Foundation.h>


@interface SomeObject : NSObject {

}
@property NSInteger aProperty;
@end

//main.m

#import <Foundation/Foundation.h>
#import "SomeObject.h"

int main (int argc, const char * argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
    [dictionary setObject:[[[SomeObject alloc] init] autorelease] forKey:@"key1"];
    [dictionary setObject:[[[SomeObject alloc] init] autorelease] forKey:@"key2"];
    [dictionary objectForKey:@"key1"].aProperty = 5; //Error HERE
    [dictionary release];

    [pool drain];
    return 0;
}

But on that line XCode gives me these errors:

error: Semantic Issue: Member reference type 'struct objc_object *' is a pointer; maybe you meant to use '->'?
error: Semantic Issue: No member named 'aProperty' in 'struct objc_object'

Can't I access a property of a returned object? (I mean, without directly calling 开发者_运维知识库the setter method)

You need to cast the returned object:

((SomeObject*)[dictionary objectForKey:@"key1"]).aProperty = 5;

or:

[(SomeObject*)[dictionary objectForKey:@"key1"] setAProperty: 5];

or:

SomeObject* obj = [dictionary objectForKey:@"key1"];
obj.aProperty = 5;