How to format ABV% in Objective-C.

ABVFormatter.h

#import <Foundation/Foundation.h>

@interface ABVFormatter : NSObject
- (NSString *)formattedABV:(NSNumber *)abv;
@end

ABVFormatter.m

#import "ABVFormatter.h"

@interface ABVFormatter ()
@property (nonatomic) NSNumberFormatter *formatter;
@end

@implementation ABVFormatter

- (NSString *)formattedABV:(NSNumber *)abv {
    self.formatter = [[NSNumberFormatter alloc] init];
    self.formatter.maximumFractionDigits = 2;
    NSString *abvString = [self.formatter stringFromNumber:abv];
    return [abvString stringByAppendingString:@"%"];
}

@end

ABVFormatterSpec.mm

#import "SpecHelper.h"

using namespace Cedar::Matchers;
using namespace Cedar::Doubles;

SPEC_BEGIN(ABVFormatterSpec)

describe(@"ABVFormatter", ^{
    __block ABVFormatter *subject;

    beforeEach(^{
        subject = [[ABVFormatter alloc] init];
    });

    describe(@"formatting an ABVr", ^{
        __block NSNumber *abv;
        __block NSString *formattedABV;

        subjectAction(^{
            formattedABV = [subject formattedABV:abv];
        });

        context(@"with an ABV with one decimal place", ^{
            beforeEach(^{
                abv = @5.3;
            });

            it(@"should only display one decimal place", ^{
                formattedABV should equal(@"5.3%");
            });
        });

        context(@"with an ABV with three decimal places", ^{
            beforeEach(^{
                abv = @5.321;
            });

            it(@"should only display the first two decimal places", ^{
                formattedABV should equal(@"5.32%");
            });
        });

        context(@"with an ABV 10% or higher", ^{
            beforeEach(^{
                abv = @15.32;
            });

            it(@"should display both digits", ^{
                formattedABV should equal(@"15.32%");
            });
        });
    });
});

SPEC_END