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up vote 6 down vote favorite
2

Right pretty new to Objective-C and iOS so right now I'm playing around with the Picker View. I've defined a person class so that when you create a Person it automatically give that person a name and age.

#import "Person.h"

@implementation Person

@synthesize personName, age;

-(id)init
{
    self = [super init];
    if(self)
    {
        personName = [self randomName];
        age = [self randomAge];
    }

    return self;
}

-(NSString *) randomName
{
    NSString* name;
    NSArray* nameArr = [NSArray arrayWithObjects: @"Jill Valentine", @"Peter Griffin", @"Meg Griffin", @"Jack Lolwut",
                            @"Mike Roflcoptor", @"Cindy Woods", @"Jessica Windmill", @"Alexander The Great",
                            @"Sarah Peterson", @"Scott Scottland", @"Geoff Fanta", @"Amanda Pope", @"Michael Meyers",
                            @"Richard Biggus", @"Montey Python", @"Mike Wut", @"Fake Person", @"Chair",
                            nil];
    NSUInteger randomIndex = arc4random() % [nameArr count];
    name = [nameArr objectAtIndex: randomIndex];
    return name;
}

-(NSInteger *) randomAge
{
    //lowerBound + arc4random() % (upperBound - lowerBound);
    NSInteger* num = (NSInteger*)(1 + arc4random() % (99 - 1));

    return num;
}

@end

Now I want to make an array of Persons so I can throw a bunch into the picker, pick one Person and show their age. First though I need to make an array of Persons. How do I make an array of objects, initialize and allocate them?

share|improve this question
3  
I was halfway through answering when iiFreeman beat me to it with the correct answer. However, i find the first name in your nameArr to be awesome :D –  Bergasms Feb 20 '13 at 0:54

3 Answers 3

up vote 17 down vote accepted 
NSMutableArray *persons = [NSMutableArray array];
for (int i = 0; i < myPersonsCount; i++) {
   [persons addObject:[[Person alloc] init]];
}
NSArray *arrayOfPersons = [NSArray arrayWithArray:persons]; // if you want immutable array

also you can reach this without using NSMutableArray:

NSArray *persons = [NSArray array];
for (int i = 0; i < myPersonsCount; i++) {
   persons = [persons arrayByAddingObject:[[Person alloc] init]];
}

One more thing - it's valid for ARC enabled environment, if you going to use it without ARC don't forget to add autoreleased objects into array! 

[persons addObject:[[[Person alloc] init] autorelease];
share|improve this answer
    
Ha, that makes sense to do. Thanks! –  Howdy_McGee Feb 20 '13 at 1:03
2  
For that second one it would be more efficient and more straight-forward to just create the mutable array and make a copy of it, vs create N new persons arrays. –  Hot Licks Feb 20 '13 at 1:04
1  
It is better form to use [persons copy] instead of arrayWithArray: IMO. (Oh, I see that the above comment is the same...sorry) –  borrrden Feb 20 '13 at 1:27
up vote 23 down vote

There is also a shorthand of doing this:

NSArray *persons = @[person1, person2, person3];

It's equivalent to 

NSArray *persons = [NSArray arrayWithObjects:person1, person2, person3, nil];

As iiFreeman said, you still need to do proper memory management if you're not using ARC.

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I tried this but I keep getting an undeclared identifier error on person1,2,3 etc. –  Howdy_McGee Feb 20 '13 at 19:59
1  
Are the objects person1, 2 and 3 declared anywhere? –  Allen Zeng Feb 20 '13 at 22:40
up vote 2 down vote

No one commenting on the randomAge method?

This is so awfully wrong, it couldn't be any wronger.

NSInteger is a primitive type - it is most likely typedef'd as int or long. In the randomAge method, you calculate a number from about 1 to 98.

You then cast that number to an NSNumber*. You had to add a cast because the compiler gave you a warning that you didn't understand. That made the warning go away, but left you with an awful bug: That number was forced to be a pointer, so now you have a pointer to an integer somewhere in the first 100 bytes of memory.

If you access an NSInteger through the pointer, your program will crash. If you write through the pointer, your program will crash. If you put it into an array or dictionary, your program will crash.

Change it either to NSInteger or int, which is probably the best, or to NSNumber if you need an object for some reason. Then create the object by calling [NSNumber numberWithInteger:99] or whatever number you want.

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