How to print an object variables from a NSMutableArray?

Question

From what I've read NSMutableArray adds objects.

How can I print the Student object variables from a given position without casting the object as a Student.

I'm looking for something like ArrayList<Student> in Java so i can easily print ArrayList.get(i).getName, ArrayList.get(i).getPrice .

    StudentRepository* myStudentRepo = [[StudentRepository alloc]init];

    Student* myStudent = [[Student alloc]init];

    myStudent.name = @"John";

    // add a Student to the NSMutableArray
    [myStudentRepo.studentRepository addObject:myStudent];

    NSLog(@"Value: %@", myStudentRepo.studentRepository);

    for(Student* myStudentItem in myStudentRepo.studentRepository)
    {
        NSLog(@"Value: %@", myStudentItem.name);
    }

    // print the Student from a given position
    NSLog(@"Value: %@", [(Student*)[myStudentRepo.studentRepository objectAtIndex:0] name]);

Thanks all for the help !

Mythul
– Mythul

2013-02-21 21:40:31 +00:00
Commented Feb 21, 2013 at 21:40 — Mythul
– Mythul, Commented Feb 21, 2013 at 21:40

rmaddy · Accepted Answer · 2013-02-21 21:31:27Z

2

The code you posted is fine as-is. There is no equivalent in Objective-C / Cocoa to Java's typed collections. You need to cast the results.

Actually, there is a little trick you can do:

NSLog(@"Value: %@", [myStudentRepo.studentRepository[0] valueForKey:@"name"]);

answered Feb 21, 2013 at 21:31

rmaddy

319k44 gold badges548 silver badges591 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

iDev Over a year ago

+1, Or it can be used as [myStudentRepo.studentRepository[0] name]. It shouldn't show any warning.

rmaddy Over a year ago

@ACB True since you end up calling name on an id object. As long as the compiler has seen a name method from somewhere, it will be happy.

Richard Brown · Accepted Answer · 2013-02-21 21:32:48Z

1

You can use KVC (Key Value Coding) to access the properties of an object without casting it:

[[myStudentRepo.studentRepository objectAtIndex:0] valueForKey:@"name"];

See: https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/KeyValueCoding/Articles/BasicPrinciples.html#//apple_ref/doc/uid/20002170-BAJEAIEE

answered Feb 21, 2013 at 21:32

Richard Brown

11.4k4 gold badges34 silver badges44 bronze badges

Comments

Mike D · Accepted Answer · 2013-02-21 21:38:16Z

1

You could override description or debugDescription in you Student class:

Since I don't the make up of your student, please allow the following example of a straight forward way:

// could also be -(NSString*)debugDescription    
- (NSString *)description {
      return [NSString stringWithFormat:@"Prop1: %@ \nIntVal1: %d\nfloatVal1 = %3.2f", self.prop1, self.intVal1, self.floatval1];
}

This gets tedious with large and complex objects, though.

answered Feb 21, 2013 at 21:38

Mike D

4,9466 gold badges46 silver badges100 bronze badges

Comments

Hossam Ghareeb · Accepted Answer · 2013-02-21 21:44:19Z

1

You Can use something like this

[(Student*)myStudentRepo.studentRepository[0] name];

Or you can override the description of the Student like this: in Student.m add this :

-(NSString *)description{
        return [NSString stringWithFormat:@"Student Name:%@", self.name];
     }

Whenever you need to print the Student just type:

NSLog(%@, student);

answered Feb 21, 2013 at 21:44

Hossam Ghareeb

7,1233 gold badges56 silver badges65 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 12:04:50Z

1

If you wish to ensure your collection actually only contains Student objects, the equivalent of Java's parametric collection you can do this. See this question for a solution for dictionaries, an array solution would be similar. You can combine the accepted solution to that question with typed getters & setters to avoid any casts.

Alternatively if you are not actually concerned over ensuring only Student objects can be added you can write an extension or category which adds a typed getter or setter - this just calls the standard setter or getter adding an casts as needed. You'll see this approach in the answers to the above question as well.

(No code here as you'll find all you need in the other question.)

edited May 23, 2017 at 12:04

CommunityBot

11 silver badge

answered Feb 21, 2013 at 21:56

CRD

53k5 gold badges73 silver badges87 bronze badges

Collectives™ on Stack Overflow

How to print an object variables from a NSMutableArray?

5 Answers 5

2 Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related