SimpleView Based app with id initWithFrame Not working - iphone

Question

I have app to create a graph i have created a view based app and then add the code for creating graph in it but it does not disply the graph. If use same code to create a separate UIView then it works other wise not
#import <UIKit/UIKit.h>
#import "ECGraph.h"
#import "ECGraphItem.h"
#class GraphsViewController;
#interface Display : UIView {
NSArray *percentages;
int myY;
ECGraph *graph;
ECGraphItem *item1;
ECGraphItem *item2;
}
#property(nonatomic,retain)NSArray*percentages;
-(void) setPercentageArray:(NSArray*) array;
#end
#import "Display.h"
#import "ECGraph.h"
#implementation Display
#synthesize percentages;
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
// Initialization code.
}
return self;
}
- (void)drawRect:(CGRect)rect {
CGContextRef _context = UIGraphicsGetCurrentContext();
graph = [[ECGraph alloc] initWithFrame:CGRectMake(500,-320,320, 200) withContext:_context isPortrait:NO];
item1 = [[ECGraphItem alloc] init];
item2 = [[ECGraphItem alloc] init];
/*
ECGraphItem *item1 = [[ECGraphItem alloc] init];
ECGraphItem *item2 = [[ECGraphItem alloc] init];*/
item1.isPercentage = YES;
item1.yValue=myY;
item1.width = 35;
item1.name = #"item1";
item2.isPercentage = YES;
item2.yValue =17;
item2.width = 35;
item2.name = #"item2";
[graph setXaxisTitle:#"name"];
[graph setYaxisTitle:#"Percentage"];
[graph setGraphicTitle:#"Histogram"];
[graph setDelegate:self];
[graph setBackgroundColor:[UIColor colorWithRed:220/255.0 green:220/255.0 blue:220/255.0 alpha:1]];
NSArray *items = [[NSArray alloc] initWithObjects:item1,item2,nil];
[graph drawHistogramWithItems:items lineWidth:2 color:[UIColor blackColor]];
}
I am adding this view in GraphsViewController but its not showing anything
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
[super viewDidLoad];
[self createGraph];
percentages = [NSArray arrayWithObjects:#"80",#"17", nil];
display = [[Display alloc] init];
[self.view addSubview:display];
[display setPercentageArray:percentages];
}

Answer 1

You should do the drawing in a separate UIView object and add it as a subview to your view controller's view. That's the way it is supposed to work.
The UIView class uses an on-demand drawing model for presenting
content.
Source: View Programming Guide for iOS
as opposed to
The UIViewController class provides the fundamental view-management
model for all iOS apps. ... A view controller manages a set of views
that make up a portion of your app’s user interface.
Source: UIViewController Class Reference
Edit:
// ...
display = [[Display alloc] init];
CGRect dFrame = CGRectMake(50, 50, 320, 200); // change these to whatever values you need
[display setFrame:dFrame];
[self.view addSubview:display];