Question

I want to develop an application in which firstly i was develop an structure code for storing X and y axis.

struct TCo_ordinates
{
float x;
float y;
};
.
Then in drawRect method i generating an object of structure like.

struct TCo_ordinates *tCoordianates; 

Now I drawing the graph of Y-Axis its code is.

    fltX1 = 30;
fltY1 = 5;
fltX2 = fltX1;
fltY2 = 270;
CGContextMoveToPoint(ctx, fltX1, fltY1);
CGContextAddLineToPoint(ctx, fltX2, fltY2);
NSArray *hoursInDays = [[NSArray alloc] initWithObjects:@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"10",@"11",@"12", nil];
for(int intIndex = 0  ; intIndex < [hoursInDays count] ; fltY2-=20, intIndex++)
{   
    CGContextSetRGBStrokeColor(ctx, 2, 2, 2, 1); 
    //CGContextSetRGBStrokeColor(ctx, 1.0f/255.0f, 1.0f/255.0f, 1.0f/255.0f, 1.0f);   
    CGContextMoveToPoint(ctx, fltX1-3 , fltY2-40);
    CGContextAddLineToPoint(ctx, fltX1+3, fltY2-40);
    CGContextSelectFont(ctx, "Helvetica", 14.0, kCGEncodingMacRoman);
    CGContextSetTextDrawingMode(ctx, kCGTextFill);
    CGContextSetRGBFillColor(ctx, 0, 255, 255, 1);
    CGAffineTransform xform = CGAffineTransformMake(
                                                    1.0,  0.0,
                                                    0.0, -1.0,
                                                    0.0,  0.0);
    CGContextSetTextMatrix(ctx, xform);
    const char *arrayDataForYAxis = [[hoursInDays objectAtIndex:intIndex] UTF8String];
    float x1 = fltX1-23;
    float y1 = fltY2-37;
    CGContextShowTextAtPoint(ctx, x1, y1, arrayDataForYAxis, strlen(arrayDataForYAxis));
    CGContextStrokePath(ctx);

Now i want to store generated the values of x1 and y1 in NSMutableArray dynamically, for that i was written the code.

NSMutableArray *yAxisCoordinates = [[NSMutableArray alloc] autorelease];
    for(int yObject = 0; yObject < intIndex; yObject++)
    {
        [yAxisCoordinates insertObject:(tCoordianates->x = x1,tCoordianates->y = y1) atIndex:yObject];  

    }

But it didn’t working. How i store the x1 and y1 values in yAxisCoordinates object.
The above code is correct?????????????

Answer 1

As far as I can see (I didn’t read the whole drawing code, just the last part), there are a few problems with your code:

1. You’re creating a new point structure where you can just use CGPoint.
2. You’re not calling init on the NSMutableArray.
3. You’re trying to insert something into the array, but it’s not a TCo_ordinates struct.
4. Even if it was, you cannot store a struct in an NSArray, you have to store an object.

Here’s one way to store a point in an NSArray:

NSMutableArray *foo = [NSMutableArray array];
NSValue * bar = [NSValue valueWithCGPoint:CGPointMake(x, y)];
[foo addObject:bar];

and you can later retrieve your point by:

CGPoint point = [[foo objectAtIndex:i] CGPointValue];