creating an object from category class

Question

I want to create a new object, one of the property is (readonly). Here is my code:

1/ My class (.h + .m)

#import <Foundation/Foundation.h>
@interface MyClass : NSObject
@property (readonly) NSString* myProperty;
@end

#import "MyClass.h"
@implementation MyClass
@end

---

2/ My class extension (.h)

#import "MyClass.h"
@interface MyClass ()
@property (readwrite) NSString* myProperty;
@end

---

3/ MyClassCategory (.h + .m)

#import "MyClass.h"

@interface MyClass (MyClassCategory)

+ (MyClass*) creatNewObject:(NSString*) mypro;

@end

#import "MyClass+MyClassCategory.h"
#import "MyClass_MyClassExtension.h"
@implementation MyClass (MyClassCategory)

+ (MyClass*) creatNewObject:(NSString*) mypro {

    MyClass* newObject = [[MyClass alloc] init];
    newObject.myProperty = mypro;
    NSLog(@"New object have been created%@", newObject);
    return newObject;
}

@end

---

#import <Foundation/Foundation.h>
#import "MyClass.h"
#import "MyClass+MyClassCategory.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSLog(@"Hello, World!");
    MyClass* newObject1 = [MyClass creatNewObject:(@"I am the new object!")];

        NSLog(@"New object have been created%@", newObject1);

    }
    return 0;
}

---

after running the code in the main method, I got

2014-09-25 21:53:52.204 MyClass[2811:303] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[MyClass setMyProperty:]: unrecognized selector sent to instance 0x100109e10'

014-09-25 22:36:05.746 MyClass[2989:303] -[MyClass setMyProperty:]: unrecognized selector sent to instance 0x100200130

I want to be enables edits to the properties of an existing class instance from category.

Can you help me please? Thank you.

Answer 1

In MyClass.m, you also need to include the extension header.

#import "MyClass_MyClassExtension.h"

Otherwise the compiler won't see myProperty is redeclared as a read-write property while generating the implementation of MyClass.