Adds animated counting support to UILabel.

Setup

Simply initialize a UICountingLabel the same way you set up a regular UILabel:

UICountingLabel* myLabel = [[UICountingLabel alloc] initWithFrame:CGRectMake(10, 10, 100, 40)];
[self.view addSubview:myLabel];

You can also add it to your XIB file, just make sure you set the class type to UICountingLabel instead of UILabel and be sure to #import "UICountingLabel.h" in the header file.

Use

Set the format of your label. This will be filled with a single int or float (depending on how you format it) when it updates:

myLabel.format = @"%d";

Alternatively, you can provide a UICountingLabelFormatBlock, which permits greater control over how the text is formatted:

myLabel.fomatBlock = ^(NSString *)(CGFloat progress) {    
    NSInteger years = value / 12;
    NSInteger months = (NSInteger)value % 12;
    if (years == 0) {
        return [NSString stringWithFormat: @"%ld months", (long)months];
    }
    else {
        return [NSString stringWithFormat: @"%ld years, %ld months", (long)years, (long)months];
    }
};

There is also a UICountingLabelAttributedFormatBlock to use an attributed string. If the formatBlock is specified, it takes precedence over the format.

Optionally, set the mode. The default is UILabelCountingMethodEaseInOut, which will start slow, speed up, and then slow down as it reaches the end. Other options are described below in the Methods section.

myLabel.method = UILabelCountingMethodLinear;

When you want the label to start counting, just call:

[myLabel countFrom:50 to:100];

You can also specify the duration. The default is 2.0 seconds.

[myLabel countFrom:50 to:100 withDuration:5.0f];

Additionally, there is animationDuration property which you can use to override the default animation duration.

myLabel.animationDuration = 1.0;

You can use common convinient methods for counting, such as:

[myLabel countFromCurrentValueTo:100];
[myLabel countFromZeroTo:100];

Behind the scenes, these convinient methods use one base method, which has the following full signature:

[myLabel     countFrom:(float)startValue 
                    to:(float)endValue 
          withDuration:(NSTimeInterval)duration];

You can get current value of your label using -currentValue method (works correctly in the process of animation too):

CGFloat currentValue = [myLabel currentValue];

Optionally, you can specify a completionBlock to perform an acton when the label has finished counting:

myLabel.completionBlock = ^{
    NSLog(@"finished counting");
};

Formats

When you set the format property, the label will look for the presence of %(.*)d or %(.*)i, and if found, will cast the value to int before formatting the string. Otherwise, it will format it using a float.

If you're using a float value, it's recommended to limit the number of digits with a format string, such as @"%.1f" for one decimal place.

Because it uses the standard stringWithFormat: method, you can also include arbitrary text in your format, such as @"Points: %i".

Modes

There are currently four modes of counting.

UILabelCountingMethodLinear

Counts linearly from the start to the end.

UILabelCountingMethodEaseIn

Ease In starts out slow and speeds up counting as it gets to the end, stopping suddenly at the final value.

UILabelCountingMethodEaseOut

Ease Out starts out fast and slows down as it gets to the destination value.

UILabelCountingMethodEaseInOut

Ease In/Out starts out slow, speeds up towards the middle, and then slows down as it approaches the destination. It is a nice, smooth curve that looks great, and is the default method.