Newbie question about strings

[yaxomoxay]

Hello - I declared a class which has an NSString object as instance variable. As an excercise, I would like to create an instance of the class and set the variable, but I am completely unable to do it.
This is the horrible code I wrote... (Started Obj C yesterday night... ).

#import <Foundation/Foundation.h>

@interface Person : NSObject
  {
    NSString *person;
  }
  -(void) SetPersonName : (NSString *) name;
  //-(NSString) GetPersonName;
@end

@implementation Person
  -(void) SetPersonName : (NSString*) name;
    {
      person = &name;
    }  
@end

int main (int argc, const char * argv[])
  {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    Person testperson;
    testperson = [Person alloc];
    testperson = [testperson init];

    NSString nametogive = @"Louis Armstrong";
    [testperson SetPersonName =nametogive];
    [pool drain];
    return 0;
  }

I get the following errors:

pollux@desktop:~/Desktop$ gcc `gnustep-config --objc-flags` -lgnustep-base stringtest.m -o eloisa
stringtest.m: In function ‘-[Person SetPersonName:]’:
stringtest.m:14: warning: assignment from incompatible pointer type
stringtest.m: In function ‘main’:
stringtest.m:22: error: statically allocated instance of Objective-C class ‘Person’
stringtest.m:22: error: statically allocated instance of Objective-C class ‘Person’
stringtest.m:23: error: incompatible types when assigning to type ‘struct Person’ from type ‘id’
stringtest.m:24: error: cannot convert to a pointer type
stringtest.m:24: error: incompatible types when assigning to type ‘struct Person’ from type ‘id’
stringtest.m:26: error: invalid initializer
stringtest.m:26: error: statically allocated instance of Objective-C class ‘NSString’
stringtest.m:26: error: statically allocated instance of Objective-C class ‘NSString’
stringtest.m:27: error: expected ‘]’ before ‘=’ token
stringtest.m:27: warning: ‘Person’ may not respond to ‘-SetPersonName’
stringtest.m:27: warning: (Messages without a matching method signature
stringtest.m:27: warning: will be assumed to return ‘id’ and accept
stringtest.m:27: warning: ‘...’ as arguments.)
stringtest.m:27: error: cannot convert to a pointer type
stringtest.m:26: warning: unused variable ‘nametogive’

It's quite obvious I am doing something wrong!

Thanks!

[yaxomoxay]

OK, I reply to myself. I just found a similar example and this is the result :

#import <Foundation/Foundation.h>

@interface Person : NSObject
  {
    NSString *person;
  }
  -(void) SetPersonName : (NSString*) name;
  //-(NSString) GetPersonName;
@end

@implementation Person
  -(void) SetPersonName : (NSString*) name;
    {
      [name retain];
      //[person release]
      person = name;
    }  
@end

int main (int argc, const char * argv[])
  {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    Person * testperson;
    testperson = [Person alloc];
    testperson = [testperson init];

    NSString * nametogive = @"Louis Armstrong";
    [testperson SetPersonName : nametogive];
    [pool drain];
    return 0;
  }

Somehow I don't get any error, I have to verify if it actually prints "Louis Armstrong". I'll let you know. One question. I don't get this passage:

-(void) SetPersonName : (NSString*) name;
    {
      [name retain];
      //[person release]
      person = name;
    }

What is the "retain" doing ?

Thanks

[hello24]

Retain releases the object - read the memory management guide from Apple.

Also, you should consider using properties - you get setters and getters for free.