ios viewcontroller view graph live with Mutable Array

Question

Good morning,

what I try to achieve is to draw a graph inside a view whilst data are being added live in the VC through an Array.

So far I have a VC and a view with its own class. Inside the class, inside drawRect I generate random numbers and they appear on the screen as dots. So far, so good.

What I want to do is generate the numbers in the ViewController (or get them via an external source), save them in a mutableArray, retrieve them inside the class and use them for the graph.

I found a similar question here on SO, from 2 years ago so there is no point commenting on it. The question was : I have on FirstViewController an array with float value. I need to pass to my View this array

The recommended solution, that was marked as working was :

In your FirstViewController.h write

#include <UIKit/UIKit.h>
extern NSArray *yourArray;

And in your FirstViewController.m write

#import "FirstViewController.h"
@interface FirstViewController ()
@end
NSArray *yourArray;

Now you'll have to import the whole FirstViewController in your "MyView"-Class. Simply #import "FirstViewController.h" in MyView.m. After doing so, "yourArray" will be available in MyView.

I do exactly what it says, then I initialize my Array, put values in it, NSLog in VC to check all working fine and it does. When I try to retrieve one value in my view and NSLog it, it says the value in the array is (null). The code is so simple I almost have nothing to show:

In my VC.h

extern NSMutableArray *yourArray;

In my VC.m implementation

NSMutableArray *yourArray;

In my VC.m viewDidLoad

NSMutableArray *yourArray = [[NSMutableArray alloc] init];
[yourArray insertObject:@"Works" atIndex:0];
NSString *object = [yourArray objectAtIndex:0];
NSLog (@"the item in Array in VC is %@", object);

In my view.m

#import "GraphViewController.h"

And then I tried adding:

NSString *object = [yourArray objectAtIndex:0];
NSLog (@"the item in Array in View is %@", object);

in (void)awakeFromNib, in (id)initWithFrame:(CGRect)frame, in (void)updateValues and in (void)drawRect:(CGRect)rect

It doesn't work from anywhere I put it. I am at a complete loss.

Could somebody please point me in the right direction ?

Thanks,

=============================================

Christian Fox Christian Fox · Accepted Answer · 2014-09-30T09:13:58

Okay so let's get the array working in the GraphViewController first and worry about the view afterwards.

It is easier to get rid of the code you used from the other stack overflow question and give you something new.

// in GraphViewController.m file
#import "GraphViewController.h"
@interface GraphViewController ()
// create a property that you can access elsewhere using self.yourArray
@property (nonatomic, strong) NSMutableArray *yourArray;
@end

@implementation GraphViewController

-(void)viewDidLoad{
    [super viewDidLoad];
    self.yourArray = [@[@"Works1",@"Works2",@"StillWorks"] mutableCopy];
    NSLog (@"the item in Array in VC is %@", self.yourArray[0]);
    NSLog (@"the item in Array in VC is %@", self.yourArray[1]);
    NSLog (@"the item in Array in VC is %@", self.yourArray[2]);
}

The View Class

// In AAAView.h declare this property
@property (nonatomic, strong) NSArray *graphDataArray;

Then when you want to pass the array from your ViewController to your view you can just do this

// yourAAAView is the instance of the view you have in your ViewController
yourAAAView.graphDataArray =  [self.dataArray copy];

//***************************************

Create an IBOutlet for your view in the GraphViewController, we'll call it "myView"
In -viewDidLoad populate yourArray with the values you need to draw the dots.
- If you are using floats, doubles or ints etc you need to wrap the values in NSNumber before they can be added to an array.
- If you are using CGPoints you need to wrap the values in NSValue before they can be added to an array
Once the array has all the values pass it to self.myView
- self.myView.graphDataArray = self.yourArray;
In YourView class -drawRect you need to get the values from self.graphDataArray and use them to draw your dots.
- Check if the self.graphDataArray is nil and return if it is. No point trying to use an non-existent array.
- I'm guessing you used a for loop originally so you will want to do something like this:

.

  for(int i = 0; i< [self.graphDataArray count]; i++) {
        // get object (NSNumber or NSValue) from array
             // NSNumber *num = self.graphDataArray[i];
             // NSValue *val = self.graphDataArray[i];
        // unwrap the value you stored in the object (float or CGpoint etc)
        // use those values to draw the dots the same way you did before
   }

ios viewcontroller view graph live with Mutable Array

3 Answers