ObjC – Getting values from Objects in array(NSMutableArray)

Question

I'm totally new to ObjC. I've already watched/read some tutorials. But now i would like to know how to make an array of objects and print out their values. I'm coming from a Java perspective. In Java it would look like this.

MyClass [] objects = new MyClass[100];

for(int i = 0; i < objects.length;i++)
   int value = i;
   objects[i] = new MyClass(value);

for(int i = 0; i < objects.length;i++)
   println(objects[i].value);

How would the equivalent in ObjC look like? I've only come that far:

NSMutableArray * objects = [NSMutableArray  arrayWithCapacity:100];

arrayWithCapacity: doesn't do what you think; it does not create an array with 100 empty slots. NSArray/NSMutableArray are not sparse arrays. — bbum
– bbum, Commented Sep 1, 2013 at 16:37

Painted Black · Accepted Answer · 2013-09-01 15:44:28Z

1

it could go something like this (take into account that it could be written more compact, but that would mystify the code for a beginner):

const int NR_ELEMENTS = 100;

NSMutableArray *objects = [NSMutableArray arrayWithCapacity:NR_ELEMENTS];

for (int i=0; i < NR_ELEMENTS; i++)
{
    MyClass *mc = [[MyClass alloc] initWith:i];
    [objects addObject:mc];
}

for (int i=0; i < NR_ELEMENTS; i++)
{
    // Suppose MyClass.value is integer
    NSLog(@"%i\n", [[objects objectAtIndex:i] value]);
}

Kind regards, PB

answered Sep 1, 2013 at 15:44

Painted Black

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2 Comments

domizai Over a year ago

So in the implementation i would do sth like: -(id) initWith:(int)n { value = n; }?

Painted Black Over a year ago

If value would be a property, then you would do [objects objectAtIndex:i].value I intended value to be a function returning a private property, hence [[objects objectAtIndex:i] value]. So you would do: -(id) initWith:(int)n { privateProperty = n; } and - (int) value { return privateProperty; }

Stocptimal · Accepted Answer · 2013-09-01 15:47:01Z

1

Not sure what your MyClass looks like, but if you wanted to add just integer objects you could do the following. Also, MutableArray resizes as needed so it is not quite like your case when you fix your array size to 100.

NSMutableArray *objects = [NSMutableArray arrayWithCapacity:100];

for(int i = 0; i < 100; ++i)
    [objects addObject:[NSNumber numberWithInt:i]];

for(id object in objects) {
    NSLog(@"%@\n",object);
}

answered Sep 1, 2013 at 15:47

Stocptimal

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1 Comment

domizai Over a year ago

I'm having two functions in the object:-(void)setAge: (int) a; -(void)setWeight: (int) w; Now i would like to set these two integers (age, weight) when i create the instances.

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