/*

 File: FahrenheitValueTransformer.m

 Abstract: Converts Kelvin units to Fahrenheit units. Leverages the

 CelsiusValueTransformer class. Supports reverse transformations.

 Version: <1.1>

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#import <Foundation/Foundation.h>

#import "FahrenheitValueTransformer.h"

@implementation FahrenheitValueTransformer

+ (Class)transformedValueClass

{

    return [NSNumber class];

}

+ (BOOL)allowsReverseTransformation

{

    return YES;   

}

- (id)transformedValue:(id)value

{

    NSValueTransformer *celsiusFromKelvinTransformer = [NSValueTransformer valueTransformerForName: @"celsiusFromKelvin"];

    value = [celsiusFromKelvinTransformer transformedValue: value]; // convert from kelvin to celsius

    if (value == nil){

        return nil;

    }

    if (![value respondsToSelector: @selector(doubleValue)]) {

        [NSException raise: NSInternalInconsistencyException

                    format: @"Value does not respond to -doubleValue.  No idea what to do. (Value is an instance of %@).",

         [value class]];

    }

    float celsiusInterimValue = [value doubleValue]; // handles NSString and NSNumber

    float fahrenheitOutputValue = (1.8 * celsiusInterimValue) + 32;

    return [NSNumber numberWithDouble: fahrenheitOutputValue];

}

- (id)reverseTransformedValue:(id)value

{

    NSValueTransformer *celsiusFromKelvinTransformer = [NSValueTransformer valueTransformerForName: @"celsiusFromKelvin"];

    if (value == nil){

        return nil;

    } 

    if (![value respondsToSelector: @selector(doubleValue)]) {

        [NSException raise: NSInternalInconsistencyException

                    format: @"Value does not respond to -doubleValue.  No idea what to do. (Value is an instance of %@).",

         [value class]];

    }

    float fahrenheitInputValue = [value doubleValue];

    float celsiusInterimValue = ((fahrenheitInputValue - 32.0) / 1.8);

    // convert from celsius to kelvin and return....

    return [celsiusFromKelvinTransformer reverseTransformedValue: [NSNumber numberWithDouble: celsiusInterimValue]];

}

@end