Drawing many strings very efficiently in Objective C - ios

Question

In a UIView occupying the entire screen I need to draw some hundred rectangles with text inside.
The UIView reacts to pan and pinch, moving and zooming the rectangles.
The text font changes according to the zooming.
I need a very fast way to draw the strings inside the rectangles. What I found so far is too slow.
I am add a test-example, the drawRect of a UIView, without zooming to be simple. It takes ~0.5 seconds on a iPad2 to draw the rectangles, which is very a long wait.
- (void)drawRect:(CGRect)rect
{
// Prepare the rectangles in which to draw the strings
// in the real app the size of the rectangles will change according to the zooming
// this takes very little time
CGRect rectangles[600] ;
float width = self.frame.size.width / 20.;
float height = self.frame.size.height / 30.;
int k = 0;
for (int i = 0; i < 20; i++)
{
for (int j = 0; j < 30; j++)
{
rectangles[k] = CGRectMake(i * width , j * height, width, height);
k++;
}
}
// In the real app, the font size will change according to the zooming
// it cannot be stored once for all
float txtSize = self.frame.size.width / 30. / 4;
NSDictionary *attributesTitle = #{NSFontAttributeName: [UIFont fontWithName:#"Verdana-bold" size:txtSize],
NSForegroundColorAttributeName: [UIColor blackColor]};
NSDictionary *attributes = #{NSFontAttributeName: [UIFont fontWithName:#"Verdana" size:txtSize],
NSForegroundColorAttributeName: [UIColor blackColor]};
NSLayoutManager *layoutManager = [[NSLayoutManager alloc] init];
NSTextContainer *textContainer = [[NSTextContainer alloc] init];
[layoutManager addTextContainer:textContainer];
NSTextStorage *textStorage ;
NSRange glyphRange;
NSLog(#"Before");
for (int i = 0; i < 600; i++)
{
// In the real app, the font size will change according to the zooming, then the textStorage is not
// first string with title
textStorage = [ [NSTextStorage alloc] initWithString:[NSString stringWithFormat:#"A:%d", i] attributes:attributesTitle];
[textStorage addLayoutManager:layoutManager];
glyphRange = [layoutManager glyphRangeForTextContainer:textContainer];
[layoutManager drawGlyphsForGlyphRange: glyphRange atPoint: rectangles[i].origin];
// second string with subtitle
textStorage = [ [NSTextStorage alloc] initWithString:[NSString stringWithFormat:#"B:%d", i] attributes:attributes];
[textStorage addLayoutManager:layoutManager];
glyphRange = [layoutManager glyphRangeForTextContainer:textContainer];
[layoutManager drawGlyphsForGlyphRange: glyphRange atPoint: CGPointMake(rectangles[i].origin.x, rectangles[i].origin.y + 10)];
}
NSLog(#"After");
}
On Android I reached a better performance, but I am not so skilled in Objective-C