Question

I developing an application in which i want to print the values on a line interval, for that i used NSArray with multiple objects and those object i passing into CGContextShowTextAtPoint() method. The code is.

             CGContextMoveToPoint(ctx, 30.0, 200.0);
     CGContextAddLineToPoint(ctx, 30.0, 440.0);
         NSArray *hoursInDays = [[NSArray alloc] initWithObjects:@"0",@"1",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"10",@"11",@"12", nil];
    int intHoursInDays = 0;
    for(float y = 400.0; y >= 200.0; y-=18, intHoursInDays++)
       {   
           CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0);   
           CGContextMoveToPoint(ctx, 28, y);
           CGContextAddLineToPoint(ctx, 32, y);
           CGContextSelectFont(ctx, "Helvetica", 12.0, 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);
           NSString *arrayDataForYAxis = [hoursInDays objectAtIndex:intHoursInDays];
           CGContextShowTextAtPoint(ctx, 10.0, y+20, [arrayDataForYAxis UTF8String], strlen((char *)arrayDataForYAxis));
           CGContextStrokePath(ctx);
                    }

The above code is executed but it given me output is {oo, 1o,2o,………..11}, i want the output is {0,1,2,3………..11,12}.
The above code given me one extra character “o” after single digit.I think the problem i meet near the parameters type casting of 5th parameter inside the method of CGContextShowTextAtpoint CGContextShowTextAtpoint(). How i resolve the problem of type casting for printing the objects of NSSArray in CGContextShowTextAtpoint() method??????????????

Answer 1

The problem is in your call to strlen. Your (char *) cast does not change the fact that it’s an NSString *.

You could change it like this:

const char *arrayDataForYAxis = [[hoursInDays objectAtIndex:intHoursInDays] UTF8String];
CGContextShowTextAtPoint(ctx, 10.0, y+20, arrayDataForYAxis, strlen(arrayDataForYAxis);