單位轉換器

units_converter

units_converter is a package written in dart for dart & flutter developers. You should not take care of unit conversion when you want to internationalize your app, everything is already done with this package! You can also add your own custom conversion!

This package is used by Converter NOW!

The documentation is structured in examples of increasing complexity. But don't worry, in most cases you will only need the first examples.

Table of Contents

• Convert a unit to another unit (the easy way)
• Convert a unit to another unit
• Convert a unit to all the another units
• Special type of conversion: numeral systems conversion
• Simple custom conversion
• Custom conversion
• Which conversions?

Convert a unit to another unit (the easy way)

Example 1: convert 1 meter in inches

// Convert 1 meter in inches
var inches = 1.convertFromTo(LENGTH.meters, LENGTH.inches);
// Print it
print(inches);

Output:

39.37007874015748

What about numeral systems? Same thing but with String:

// Convert '8B' hexadecimal to octal
var octal = '8B'.convertFromTo(NUMERAL_SYSTEMS.hexadecimal, NUMERAL_SYSTEMS.octal);
// Print it
print(octal);

Output:

213

Note: most of the time is what you need, use this method if you just want to convert a unit in another unit. BUT, it is not recommended if you want to convert a unit to multiple units, or if you are interested in the symbol of a unit or if you are interested in the format of the string representation of the value (significant figures, scientific notation, etc.).

Convert a unit to another unit

Example 2: convert 1 meter in inches

// We give 1 meter as input
var length = Length()..convert(LENGTH.meters, 1);
// We get the inches
var unit = length.inches;
// We print the Unit
print('name:${unit.name}, value:${unit.value}, stringValue:${unit.stringValue}, symbol:${unit.symbol}');

Output:

name:LENGTH.inches, value:39.370078740157474, stringValue:39.37007874, symbol:in

Convert a unit to all the another units

Example 3: convert 1 degree in all the other angles units. This time we want also to specify that we just want 7 significant figures and we don't want trailing zeros (e.g. 1.000000 -> 1).

// Initialization of the object
var angle = Angle(significantFigures: 7, removeTrailingZeros: false); // conversion
angle.convert(ANGLE.degree, 1);
// We get all the units
var units = angle.getAll(); //We get all ther others units
// Let's print all of them
for (var unit in units) {
  print('name:${unit.name}, value:${unit.value}, stringValue:${unit.stringValue}, symbol:${unit.symbol}');
}

Output:

name:ANGLE.degree, value:1.0, stringValue:1.000000, symbol:°
name:ANGLE.minutes, value:60.0, stringValue:60.00000, symbol:'
name:ANGLE.seconds, value:3600.0, stringValue:3600.000, symbol:''

As you can see in this example if you specify removeTrailingZeros: false, the stringValue keeps all the trailing zeros (the default is true). You can also ask for an certain number of significant figures in the stringValue.

Special type of conversion: numeral systems conversion

Warning! Numeral systems conversion is the only conversion that need the input as a String, and not as a double / int for obvious reasons

Example 4: convert '100' (decimal) to binary and hexadecimal

// We give '100' decimal as input
var numeralSystems = NumeralSystems()..convert(NUMERAL_SYSTEMS.decimal, '100');
// We get the binary value
print('Binary: ${numeralSystems.binary.stringValue}');
// We get the hexadecimal value
print('Hexadecimal: ${numeralSystems.hexadecimal.stringValue}'); 

Output:

Binary: 1100100
Hexadecimal: 64

Simple custom conversion

Use SimpleCustomProperty when you are dealing with a linear conversion between the units, i.e. when a unit is x times a value. In SimpleCustomProperty we have to define a conversionMap between a base unit, which must have a value of 1, and all the other units. In the example below we say that 1€ is 1.2271$, but also 0.9033₤, and so on and so forth.

Example 5: define the currency exchange rate with their symbols (optional) and perform the conversion between two of them.

final Map<String, double> conversionMap = {
  'EUR': 1,
  'USD': 1.2271,
  'GBP': 0.9033,
  'JPY': 126.25,
  'CNY': 7.9315,
};
// The map of the symbols is optional but nice
final Map<String, String> mapSymbols = {
  'EUR': '€',
  'USD': '\$',
  'GBP': '₤',
  'JPY': '¥',
  'CNY': '¥',
};

var customConversion = SimpleCustomProperty(conversionMap, mapSymbols: mapSymbols);
customConversion.convert('EUR', 1);
Unit usd = customConversion.getUnit('USD');
print('1€ = ${usd.stringValue}${usd.symbol}');

Output:

1€ = 1.2271$

Custom conversion

In most cases, you will only need SimpleCustomProperty (see the previous section). SimpleCustomProperty allow you to define conversions in the form of y=ax. But if you need to define special relationship between units you need CustomProperty. This allow you to perform conversion like: y=ax+b and y=a/x+b (where y and x are the value of two units and a and b are two coefficient), for example the conversion between Celsius and Fahrenheit use the first relation and the conversion between km/l and l/100km has to be done with the second relation. Both can't be done with SimpleCustomProperty.

Example 6: let's define the following imaginary units of measurement:

• KiloDash = 1000 * Dash
• DashPlus1 = Dash + 1
  • OneOver(DashPlus1) = 1 / (DashPlus1)

As you can see all this relations can be structured like a conversion tree. Now you can take a look at the example below: it does in the code what we have just said.

ConversionNode conversionTree = ConversionNode(
  name: 'Dash',
  children: [
    ConversionNode(
      name: 'KiloDash',
      coefficientProduct: 1000,
    ),
    ConversionNode(
      name: 'DashPlus1',
      coefficientSum: -1,
      children: [
        ConversionNode(
          name: 'OneOver(DashPlus1)',
          conversionType: ConversionType.reciprocalConversion,
        ),
      ],
    ),
  ],
);
final Map<String, String> symbolsMap = {
  'Dash': 'dsh',
  'KiloDash': 'kdsh',
};
var dash = CustomProperty(
  conversionTree: conversionTree,
  mapSymbols: symbolsMap,
  name: 'Conversion of Dash',
);
dash.convert('Dash', 1);
var myUnits = dash.getAll();
for (var unit in myUnits) {
  print('name:${unit.name}, value:${unit.value}, stringValue:${unit.stringValue}, symbol:${unit.symbol}');
}

Output:

name:Dash, value:1.0, stringValue:1, symbol:dsh
name:KiloDash, value:0.001, stringValue:0.001, symbol:kdsh
name:DashPlus1, value:2.0, stringValue:2, symbol:null
name:OneOver(DashPlus1), value:0.5, stringValue:0.5, symbol:null

Which conversions?

• Amount of substance (moles, millimoles, etc.)
• Angles (degree, radians, etc.)
• Area (hectares, acres, etc.)
• Digital data (byte, gigabit, etc.)
• Density (grams per liter, micrograms per milliliter, etc.)
• Energy (Joule, kilowatt-hour, etc.)
• Force (Newton, kilogram-force, etc.)
• Fuel consumption (miles per hour, kilometers per hour, etc.)
• Length (meter, miles, etc)
• Mass (kilograms, ounces, etc.)
• Molar mass (grams per mole, milligrams per millimole, etc.)
• Molar mass (moles per cubic meter, moles per liter, etc.)
• Numeral systems (hexadecimal, binary, etc.)
• Power (kilowatt, horse power, etc.)
• Pressure (bar, psi, etc.)
• Reciprocal of molar mass (moles per gram, etc.)
• Shoe size (eu size, us size, etc.)
• SI prefixes (giga, tera, etc.)
• Speed (miles per hour, kilometers per hour, etc.)
• Temperature (celsius, fahrenheit, etc.)
• Time (seconds, years, etc.)
• Torque (newtons per meter, dyne meter, etc.)
• Volume (liter, cubic meters, etc.)