这些人找到了解决方案:

These people found a solution:

http://www.11pixel.com/blog/28/resize-multi-line-text-to-fit-uilabel-on-iphone/

他们的解决方案如下:

int maxDesiredFontSize = 28;
int minFontSize = 10;
CGFloat labelWidth = 260.0f;
CGFloat labelRequiredHeight = 180.0f;
//Create a string with the text we want to display.
self.ourText = @"This is your variable-length string. Assign it any way you want!";

/* This is where we define the ideal font that the Label wants to use.
   Use the font you want to use and the largest font size you want to use. */
UIFont *font = [UIFont fontWithName:@"Marker Felt" size:maxDesiredFontSize];

int i;
/* Time to calculate the needed font size.
   This for loop starts at the largest font size, and decreases by two point sizes (i=i-2)
   Until it either hits a size that will fit or hits the minimum size we want to allow (i > 10) */
for(i = maxDesiredFontSize; i > minFontSize; i=i-2)
{
    // Set the new font size.
    font = [font fontWithSize:i];
    // You can log the size you're trying: NSLog(@"Trying size: %u", i);

    /* This step is important: We make a constraint box 
       using only the fixed WIDTH of the UILabel. The height will
       be checked later. */ 
    CGSize constraintSize = CGSizeMake(labelWidth, MAXFLOAT);

    // This step checks how tall the label would be with the desired font.
    CGSize labelSize = [self.ourText sizeWithFont:font constrainedToSize:constraintSize lineBreakMode:UILineBreakModeWordWrap];

    /* Here is where you use the height requirement!
       Set the value in the if statement to the height of your UILabel
       If the label fits into your required height, it will break the loop
       and use that font size. */
    if(labelSize.height <= labelRequiredHeight)
        break;
}
// You can see what size the function is using by outputting: NSLog(@"Best size is: %u", i);

// Set the UILabel's font to the newly adjusted font.
msg.font = font;

// Put the text into the UILabel outlet variable.
msg.text = self.ourText;

为了让它工作，必须在界面构建器中将 IBOutlet 分配给 UILabel.

In order to get this working, a IBOutlet must be assigned in the interface builder to the UILabel.

"IBOutlet UILabel *msg;"

"IBOutlet UILabel *msg;"

所有的优点都是 11 像素的人.

All the merit is of the people at 11pixel.