Force NSMeasurementFormatter to get value over 1 with NSMeasurementFormatterUnitOptionsNaturalScale optiion

Question

If we put the value 100g into a NSUnit and use NSMeasurementFormatterUnitOptionsNaturalScale to get a translated String, the result is 3.52 oz for Imperial system. The problem is with Metric, the result is 0,1 kg which is the good value but i need to keep 100g. It's for a recipe and and it's more common to keep "g" when the value is below 1 kg.

Tested with meters the problem don't exist, 100m is 100m in metric probably because meter is the base value like kg (and not g).

Is there a way to force it to have a value over 1 instead of 0,xx ?

NSUnitMass *g = [NSUnitMass grams];
NSMeasurement *measurementGramm = [[NSMeasurement alloc] initWithDoubleValue:100 unit:g];
NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];
[formatter setUnitOptions:NSMeasurementFormatterUnitOptionsNaturalScale];
NSLog(@"NSMeasurementFormatterUnitOptionsNaturalScale ---------- %@", [formatter stringFromUnit:g]);

This code in this article is in Swift, but it might give you an idea of how to tackle the problem - https://medium.com/@pwilko/scaling-measurement-in-swift-71f3c1856458 — Paulw11, Mar 12 '20 at 01:06

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

To make it easier, I assume that stored value is based on kg.

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:0.1 unit:NSUnitMass.kilograms];
NSLog(@"Measurement value = %@", measurement);

NSLog result

Measurement value = <NSMeasurement: 0x28028ada0> value: 0.100000 unit: kg

Here we can see that we have a value of 0.1 and unit in kg.

It's for a recipe and and it's more common to keep "g" when the value is below 1 kg.

We can convert the unit if the value is below 1

NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];

NSLog(@"Locale (KG) measurement value = %@", [formatter stringFromMeasurement:measurement]);

if (measurement.doubleValue < 1.0) {
    NSLog(@"Locale (G) measurement value = %@", [formatter stringFromMeasurement:[measurement measurementByConvertingToUnit:NSUnitMass.grams]]);
} else {
    NSLog(@"Locale (KG) measurement value = %@", [formatter stringFromMeasurement:measurement]);
}

NSLog result

Locale (KG) measurement value = 0,1 kg
Locale (G) measurement value = 0,1 kg

The result is still in kg, this is caused by unitOptions

By default, if unitOptions is set to the empty set, the formatter will do the following:

kilocalories may be formatted as "C" instead of "kcal" depending on the locale.

kilometersPerHour may be formatted as "miles per hour" for US and UK locales but "kilometers per hour" for other locales.

We just have to change that

formatter.unitOptions = NSMeasurementFormatterUnitOptionsProvidedUnit;

if (measurement.doubleValue < 1.0) {
    NSLog(@"Locale (G) measurement value = %@", [formatter stringFromMeasurement:[measurement measurementByConvertingToUnit:NSUnitMass.grams]]);
} else {
    NSLog(@"Locale (KG) measurement value = %@", [formatter stringFromMeasurement:measurement]);
}

NSLog result

Locale (G) measurement value = 100 g

Full code

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:0.1 unit:NSUnitMass.kilograms];
NSLog(@"Measurement value = %@", measurement);

NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];

NSLog(@"Locale (KG) measurement value = %@", [formatter stringFromMeasurement:measurement]);

if (measurement.doubleValue < 1.0) {
    NSLog(@"Locale (G) measurement value = %@", [formatter stringFromMeasurement:[measurement measurementByConvertingToUnit:NSUnitMass.grams]]);
} else {
    NSLog(@"Locale (KG) measurement value = %@", [formatter stringFromMeasurement:measurement]);
}

formatter.unitOptions = NSMeasurementFormatterUnitOptionsProvidedUnit;

if (measurement.doubleValue < 1.0) {
    NSLog(@"Locale (G) measurement value = %@", [formatter stringFromMeasurement:[measurement measurementByConvertingToUnit:NSUnitMass.grams]]);
} else {
    NSLog(@"Locale (KG) measurement value = %@", [formatter stringFromMeasurement:measurement]);
}

The math is fine but i can't imagine how many lines of code i need to use if i must test every value for different unit (g, kg, ml, oz...). The NSMeasurementFormatterUnitOptionsNaturalScale should have a option to get the prefered format since it convert the value in a more natural readable format — hbdev, Mar 23 '20 at 12:37

Force NSMeasurementFormatter to get value over 1 with NSMeasurementFormatterUnitOptionsNaturalScale optiion

1 Answers1