How do I parse through an array of objects in Objective-C?

Question

Coming from C++, here's my question :

I have created objects of this type :

    Size *one = [[Size alloc] initWithX: 3 andY: 1];
    Size *two = [[Size alloc] initWithX: 4 andY: 7];
    // etc...
    Size *thirtythree = [[Size alloc] initWithX: 5 andY: 9];

( with a @property int x; & @property int y; for each object.. )

that I have stored in an array as follows :

NSArray *arrayOfSizes;

arrayOfSizes = [NSArray arrayWithObjects:one,two,three,four,five,six,
                seven,eight,nine,ten,eleven,twelve,thirteen,
                fourteen,fifteen,sixteen,seventeen,eighteen,
                nineteen,twenty,twentyone,twentytwo,
                twentythree,twentyfour,twentyfive,twentysix,
                twentyseven,twentyeight,twentynine,thirty,
                thirtyone,thirtytwo,thirtythree nil];

now I have a single object of type :

Myobject *myObject = [[Myobject alloc] initWithX: 5 andY: 3];

that also has a @property int x; & @property int y; ...

and I want to compare its values to the values of the objects found in the array, until I find an array object of similar values.. But I don't know how to do that in Obj-C. (in c++ I would simply use a vector v; with v.size(); and v[x]; ..etc... I suppose..)

here's what I'm looking for.. :)

while( !wholeOfArrayOfSizesChecked && !found)
{
    if ( // x & y of object in array is equal to x & y of myObject )
    {
        found = YES;
    }
    else if( // whole of array checked)
    {
       wholeOfArrayOfSizesChecked = YES;
    }
    else
    { 
      //move on to the next object of the array..
    }
}

Thanks in advance for any help!

Alladinian · Accepted Answer · 2012-08-09 14:36:44Z

2

Well, you could just use fast enumeration on the array. Something like this:

Myobject *myObject = [[Myobject alloc] initWithX: 5 andY: 3];

for (Size *s in arrayOfSizes)
{
    if (s.x == myObject.x && s.y == myObject.y)
    {
        // Found one
        // Do something useful...
        break;
    }
}

edited Aug 9, 2012 at 14:36

answered Aug 9, 2012 at 14:25

Alladinian

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2 Comments

user1073400 Over a year ago

according to documentation, the only problem with that is that once you break from the loop, the pointer stays pointing at the last object that was being checked. So next time I go into that for loop it won't start checking from the very top if I understand correctly...

Alladinian Over a year ago

@SproutCoder No that is not true. Every time you run this loop the array will be enumerated from the first element. If you had declared your s before the loop, then it would have the last value before the break (in my example s is scoped inside the loop). But even then, the next time you'd go inside the loop the array would be enumerated again from its start. I hope that this makes sense.

Paul.s · Accepted Answer · 2012-08-09 14:38:42Z

1

Another one:

NSUInteger index = [arrayOfSizes indexOfObjectPassingTest:
    ^BOOL(Size *s, NSUInteger idx, BOOL *stop)
    {
        return (s.x == myObject.x) && (s.y == myObject.y);
    }
];

if (index != NSNotFound) {
    id object = [arrayOfSizes objectAtIndex:index];
}

edited Aug 9, 2012 at 14:38

Paul.s

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answered Aug 9, 2012 at 14:35

Martin R

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Comments

Hermann Klecker · Accepted Answer · 2012-08-10 07:37:55Z

0

Just to use your given structure. There are smarter ways of doing it though :)

wholeOfArrayOfSizesChecked = NO; 
int currObj = 0  
while( !wholeOfArrayOfSizesChecked && !found)
{
    Size *current = (Size *)[arrayOfSizes objectAtIndex:i];
    if (myObject.x == current.x && myObject.y == current.y)
    {
        found = YES;
    }
    else if(currObj == [arrayOfSizes count] -1 )
    {
       wholeOfArrayOfSizesChecked = YES;
    }
    else
    { 
      currObj++;
    }
}

edited Aug 10, 2012 at 7:37

answered Aug 9, 2012 at 14:31

Hermann Klecker

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2 Comments

user1073400 Over a year ago

I'm using beyerss for loop but his [arrayOfSizes size] gives an error.. Could I simply replace that with your [arrayOfSizes count] -1 and use the following : for (int i = 0; i < [arrayOfSizes count]-1; i++) ?

Hermann Klecker Over a year ago

@SproutCoder, yes, you can do that.

beyerss · Accepted Answer · 2012-08-09 14:25:39Z

0

Try something like this:

for (int i = 0; i < [arrayOfSizes size]; i++)
{
  Size *current = (Size *)[arrayOfSizes objectAtIndex:i];
  if (myObject.x == current.x && myObject.y == current.y)
  {
    // found
    break;
  }
}

answered Aug 9, 2012 at 14:25

beyerss

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2 Comments

user1073400 Over a year ago

hmm... I get a no visible NSArray declares the selector 'size'

beyerss Over a year ago

replace size with count. Just a little work on your own and you would have seen that.

score 0 · Accepted Answer · 2012-08-09 14:28:49Z

0

How'bout a for-in loop?

for (Size *item in array) {
   // compare 'item' to myObject
   if (/* equal condition here */) break;
}

edited Aug 9, 2012 at 14:28

answered Aug 9, 2012 at 14:23

user529758

Comments

The dude · Accepted Answer · 2012-08-09 15:47:53Z

0

-(BOOL) isSize:(Size*)size equalToMyObject:(MyObject*)object{
    return (size.x == object.x) && (size.y == object.y);
}

//In some method where you are checking it:
for (Size* size in arrayOfSizes){
        if ([self isSize:size equalToMyObject:myObject]){
            //You found it! They're equal!
            break;
        }
}

edited Aug 9, 2012 at 15:47

answered Aug 9, 2012 at 14:30

The dude

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1 Comment

Martin R Over a year ago

& should be && in the comparison function.

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