repo_zf1/documentation/manual/en/module_specs/Zend_Measure-Edit.xml

<?xml version="1.0" encoding="UTF-8"?>
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<sect1 id="zend.measure.edit">
    <title>Manipulating Measurements</title>

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

    <itemizedlist>
        <listitem>
            <para>
                <link linkend="zend.measure.edit.convert"><code>Convert</code></link>
            </para>
        </listitem>

        <listitem>
            <para>
                <link linkend="zend.measure.edit.add"><code>Add and subtract</code></link>
            </para>
        </listitem>

        <listitem>
            <para>
                <link linkend="zend.measure.edit.equal"><code>Compare to boolean</code></link>
            </para>
        </listitem>

        <listitem>
            <para>
                <link
                    linkend="zend.measure.edit.compare"><code>Compare to
                    greater/smaller</code></link>
            </para>
        </listitem>

        <listitem>
            <para>
                <link
                    linkend="zend.measure.edit.changevalue"><code>Manually change
                    values</code></link>
            </para>
        </listitem>

        <listitem>
            <para>
                <link
                    linkend="zend.measure.edit.changetype"><code>Manually change types</code></link>
            </para>
        </listitem>
    </itemizedlist>

    <sect2 id="zend.measure.edit.convert">
        <title>Convert</title>

        <para>
            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
            <methodname>convertTo()</methodname>. 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.
        </para>

        <para>
            The <code>convertTo</code> method accepts an optional parameter. With this parameter you
            can define an precision for the returned output. The standard precision is
            '<code>2</code>'.
        </para>

        <example id="zend.measure.edit.convert.example-1">
            <title>Convert</title>

            <programlisting language="php"><![CDATA[
$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);

// define a precision for the output
print "Ton:".$unit->convertTo(Zend_Measure_Weight::TON, 3);
]]></programlisting>
        </example>
    </sect2>

    <sect2 id="zend.measure.edit.add">
        <title>Add and subtract</title>

        <para>
            Measurements can be added together using <methodname>add()</methodname> and subtracted
            using <methodname>sub()</methodname>. 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.
        </para>

        <para>
            <example id="zend.measure.edit.add.example-1">
                <title>Adding units</title>

                <programlisting language="php"><![CDATA[
// 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"
]]></programlisting>
            </example>
        </para>

        <note>
            <title>Automatic conversion</title>

            <para>
                Adding one object to another will automatically convert it to the correct unit. It
                is not necessary to call <link
                    linkend="zend.measure.edit.convert"><methodname>convertTo()</methodname></link>
                before adding different units.
            </para>
        </note>

        <para>
            <example id="zend.measure.edit.add.example-2">
                <title>Subtract</title>

                <para>
                    Subtraction of measurements works just like addition.
                </para>

                <programlisting language="php"><![CDATA[
// 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;
]]></programlisting>
            </example>
        </para>
    </sect2>

    <sect2 id="zend.measure.edit.equal">
        <title>Compare</title>

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

        <para>
            <example id="zend.measure.edit.equal.example-1">
                <title>Different measurements</title>

                <programlisting language="php"><![CDATA[
// 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";
}
]]></programlisting>
            </example>

            <example id="zend.measure.edit.equal.example-2">
                <title>Identical measurements</title>

                <programlisting language="php"><![CDATA[
// 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";
}
]]></programlisting>
            </example>
        </para>
    </sect2>

    <sect2 id="zend.measure.edit.compare">
        <title>Compare</title>

        <para>
            To determine if a measurement is less than or greater than another, use
            <methodname>compare()</methodname>, 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.
        </para>

        <para>
            <example id="zend.measure.edit.compare.example-1">
                <title>Difference</title>

                <programlisting language="php"><![CDATA[
$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);
]]></programlisting>
            </example>
        </para>
    </sect2>

    <sect2 id="zend.measure.edit.changevalue">
        <title>Manually change values</title>

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

        <para>
            <example id="zend.measure.edit.changevalue.example-1">
                <title>Changing a value</title>

                <programlisting language="php"><![CDATA[
$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;
]]></programlisting>
            </example>
        </para>
    </sect2>

    <sect2 id="zend.measure.edit.changetype">
        <title>Manually change types</title>

        <para>
            To change the type of a measurement without altering its value use
            <methodname>setType()</methodname>.
        </para>

        <example id="zend.measure.edit.changetype.example-1">
            <title>Changing the type</title>

            <programlisting language="php"><![CDATA[
$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"
]]></programlisting>
        </example>
    </sect2>
</sect1>
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