21.4. Manipulating Measurements

21.4. Manipulating Measurements
Terug	Hoofdstuk 21. Zend_Measure	Volgende

Parsing and normalization of input, combined with output to localized notations makes data accessible to users in different locales. Many additional methods exist in Zend_Measure_* components to manipulate and work with this data, after it has been normalized.

21.4.1. Convert

Probably the most important feature is the conversion into different units of measurement. The conversion of a unit can be done any number of times using the method convertTo(). Units of measurement can only be converted to other units of the same type (class). Therefore, it is not possible to convert (e.g.) a length into a weight, which would might encourage poor programming practices and allow errors to propagate without exceptions.

Voorbeeld 21.10. Convert

<?php
require_once 'Zend/Measure/Weight.php';

$locale = new Zend_Locale('de');
$mystring = "1.234.567,89";
$unit = new Zend_Measure_Weight($mystring,'POND', $locale);

print "Kilo:".$unit->convertTo('KILOGRAM');

// constants are considered "better practice" than strings
print "Ton:".$unit->convertTo(Zend_Measure_Weight::TON);
?>

21.4.2. Add and subtract

Measurements can be added together using add() and subtracted using sub(). Each addition will create a new object for the result. The actual object will never be changed by the class. The new object will be of the same type as the originating object. Dynamic objects support a fluid style of programming, where complex sequences of operations can be nested without risk of side-effects altering the input objects.

Voorbeeld 21.11. Adding units

<?php
require_once 'Zend/Measure/Length.php';

// Define objects
$unit = new Zend_Measure_Length(200, Zend_Measure_Length::CENTIMETER);
$unit2 = new Zend_Measure_Length(1, Zend_Measure_Length::METER);

// Add $unit2 to $unit 
$sum = $unit->add($unit2);

echo $sum; // outputs "300 cm"
?>

	Automatic conversion
	Adding one object to another will automatically convert it to the correct unit. It is not neccessary to call `convertTo()` before adding different units.

Voorbeeld 21.12. Subtract

Subtraction of measurements works just like addition.

<?php
require_once 'Zend/Measure/Length.php';

// Define objects
$unit = new Zend_Measure_Length(200, Zend_Measure_Length::CENTIMETER);
$unit2 = new Zend_Measure_Length(1, Zend_Measure_Length::METER);

// Subtract $unit2 from $unit
$sum = $unit->sub($unit2);

echo $sum;
?>

21.4.3. Compare

Measurements can also be compared, but without automatic unit conversion. Thus, equals() returns TRUE, only if both the value and the unit of measure are identical.

Voorbeeld 21.13. Different measurements

<?php
require_once 'Zend/Measure/Length.php';

// Define measurements
$unit = new Zend_Measure_Length(100, Zend_Measure_Length::CENTIMETER);
$unit2 = new Zend_Measure_Length(1, Zend_Measure_Length::METER);

if ($unit->equals($unit2)) {
    print "Both measurements are identical";
} else {
    print "These are different measurements";
}
?>

Voorbeeld 21.14. Identical measurements

<?php
require_once 'Zend/Measure/Length.php';

// Define measurements
$unit = new Zend_Measure_Length(100, Zend_Measure_Length::CENTIMETER);
$unit2 = new Zend_Measure_Length(1, Zend_Measure_Length::METER);

$unit2->setType(Zend_Measure_Length::CENTIMETER);

if ($unit->equals($unit2)) {
    print "Both measurements are identical";
} else {
    print "These are different measurements";
}
?>

21.4.4. Compare

To determine if a measurement is less than or greater than another, use compare(), which returns 0, -1 or 1 depending on the difference between the two objects. Identical measurements will return 0. Lesser ones will return a negative, greater ones a positive value.

Voorbeeld 21.15. Difference

<?php
require_once 'Zend/Measure/Length.php';

$unit = new Zend_Measure_Length(100, Zend_Measure_Length::CENTIMETER);
$unit2 = new Zend_Measure_Length(1, Zend_Measure_Length::METER);
$unit3 = new Zend_Measure_Length(1.2, Zend_Measure_Length::METER);

print "Equal:".$unit2->compare($unit);
print "Lesser:".$unit2->compare($unit3);
print "Greater:".$unit3->compare($unit2);
?>

21.4.5. Manually change values

To change the value of a measurement explicitly, use setValue(). to overwrite the current value. The parameters are the same as the constructor.

Voorbeeld 21.16. Changing a value

<?php
require_once 'Zend/Measure/Length.php';

$locale = new Zend_Locale('de_AT');
$unit = new Zend_Measure_Length(1,Zend_Measure_Length::METER);

$unit->setValue(1.2);
echo $unit;

$unit->setValue(1.2, Zend_Measure_Length::KILOMETER);
echo $unit;

$unit->setValue("1.234,56", Zend_Measure_Length::MILLIMETER,$locale);
echo $unit;
?>

21.4.6. Manually change types

To change the type of a measurement without altering its value use setType().

Voorbeeld 21.17. Changing the type

<?php
require_once 'Zend/Measure/Length.php';

$unit = new Zend_Measure_Length(1,Zend_Measure_Length::METER);
echo $unit; // outputs "1 m"

$unit->setType(Zend_Measure_Length::KILOMETER);
echo $unit; // outputs "1000 km"
?>

Terug	Omhoog	Volgende
21.3. Outputting measurements	Begin	21.5. Types of measurements