Retrieve an array from a Parent View Controller in a subview

Question

So I seem to have spent the last couple of days trying to find various solutions for this and have decided it's probably best that I just ask someone. I'm using a storyboard and I send an array from one ViewController to another just fine. But once in this SecondViewController i'm having an issue with it. I would then like to be able to access the array in a subview of this view controller to be able to draw a graph with the data but whenever I try I just always get null from the code in the subview even though it's definitely in the ParentViewController. Could someone please have a look at my current code and let me know how I would get this data in my subview.

ParentViewController.h

#import <UIKit/UIKit.h>
#import "GraphView.h"
#import "Model.h"
@interface GraphViewController : UIViewController
 @property (strong) Model *model;
 @property (weak) GraphView *graph;
 @property (strong) NSArray *data;
@end

ParentViewController.m

#import "GraphViewController.h"

@interface GraphViewController ()

@end

@implementation GraphViewController
@synthesize graph;
- (void)viewDidLoad {
   [super viewDidLoad];
   // Do any additional setup after loading the view.
    NSLog(@"Model data: %@",self.data);//prints just fine
[self.graph setNeedsDisplay];
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

SubView.h

 #import <UIKit/UIKit.h>
 #import "Model.h"
 @interface GraphView : UIView 
 @property (weak) NSArray *array;
 @property (strong) Model *model;
 @end

Subview.m

 #import "GraphView.h"
 #import "GraphViewController.h"
 @implementation GraphView
- (id)initWithFrame:(CGRect)frame dataArray:(NSArray*)data {
   self = [super initWithFrame:frame];
   if (self) {
    // Initialization code
    }
return self;
 }
- (void)drawRect:(CGRect)rect {
   // Drawing code
    NSLog(@"Draw Rect");
    NSLog(@"%@", self.array);//The bit that keeps returning null
    if (self.array != nil){
       NSLog(@"Drawing Rect");
       CGContextRef ctx = UIGraphicsGetCurrentContext();
       CGContextBeginPath(ctx);
       CGContextMoveToPoint(ctx, 160, 100);
       CGContextAddLineToPoint(ctx,260,300);
       CGContextAddLineToPoint(ctx,60,300);
       CGContextClosePath(ctx);
       [[UIColor blueColor] setFill];
       [[UIColor greenColor] setStroke];
       CGContextSetLineWidth(ctx,2.0);
       CGContextDrawPath(ctx,kCGPathFillStroke);
    }

 }

Now I know that it would return null now because i'm not actually assigning it to anything but i've tried so many different ways of trying to assign it to the data array in the parent view controller i've forgotten how i even started. Any help would be much appreciated!

Answer 1

There is 3 issues in your code:

1. @property (weak) GraphView *graph; // graph is weak, the object will be released after the assignment.
2. No assignment for self.array in the GraphView.
3. Didn't add the graph into the controller.view.subviews.

Here is my code:

@interface GraphViewController : UIViewController

@property (strong) Model *model;
@property (retain) GraphView *graph; // change to retain
@property (strong) NSArray *data;
@end

@implementation GraphViewController

@synthesize graph;
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    self.data = [[NSArray alloc] initWithObjects:@1, @2, nil];

    self.graph = [[GraphView alloc] initWithFrame:CGRectMake(0, 0, 320, 320) dataArray:self.data];

    [self.view addSubview:self.graph];  // Init graph and add into subviews.
}
@end

@interface GraphView : UIView

- (id)initWithFrame:(CGRect)frame dataArray:(NSArray*)data;

@property (weak) NSArray *array;
@property (strong) Model *model;
@end

@implementation GraphView

- (id)initWithFrame:(CGRect)frame dataArray:(NSArray*)data {
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code

        self.array = data; // Assign the array.
    }
    return self;
}
- (void)drawRect:(CGRect)rect {
    // Drawing code
    NSLog(@"Draw Rect");
    NSLog(@"%@", self.array);//The bit that keeps returning null
    if (self.array != nil){
        NSLog(@"Drawing Rect");
        CGContextRef ctx = UIGraphicsGetCurrentContext();
        CGContextBeginPath(ctx);
        CGContextMoveToPoint(ctx, 160, 100);
        CGContextAddLineToPoint(ctx,260,300);
        CGContextAddLineToPoint(ctx,60,300);
        CGContextClosePath(ctx);
        [[UIColor blueColor] setFill];
        [[UIColor greenColor] setStroke];
        CGContextSetLineWidth(ctx,2.0);
        CGContextDrawPath(ctx,kCGPathFillStroke);
    }   
}
@end

Answer 2

Assign GraphView's data in viewDidLoad. Also make sure that your self.graph is properly connected/initialized.

- (void)viewDidLoad {
   [super viewDidLoad];
   // Do any additional setup after loading the view.
   NSLog(@"Model data: %@",self.data);//prints just fine
   self.graph.array = self.data;
   [self.graph setNeedsDisplay];
}