Groovyのwith
3563 ワード
in Java
in Groovy:
各Groovy閉パッケージには、それに関連するdelegate(エージェント)がある.
書き方を変えます.
Another bit of info that is missing here is the strategy that a closure uses to decide when to send method calls to the delegate. Each Groovy closure has a resolveStrategy associated with it. This property determines how/if the delegate comes in to play. The 4 possible values for the resolveStrategy are OWNER_FIRST, DELEGATE_FIRST, OWNER_ONLY and DELEGATE_ONLY (all constants defined in groovy.lang.Closure). The default is OWNER_FIRST. Consider the owner to be the "this"wherever the closure is defined. Here is a simple example...
実行結果:
ソース:
http://java.dzone.com/news/getting-groovy-with-with
// PrintIndependenceDay.java
import java.util.Calendar;
import java.util.Date;
public class PrintIndependenceDay {
public static void main(String[] args) {
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.set(Calendar.MONTH, Calendar.JULY);
calendar.set(Calendar.DATE, 4);
calendar.set(Calendar.YEAR, 1776);
Date time = calendar.getTime();
System.out.println(time);
}
}
in Groovy:
// PrintIndependenceDay.groovy
def calendar = Calendar.instance
calendar.with {
clear()
set MONTH, JULY
set DATE, 4
set YEAR, 1776
println time
}
各Groovy閉パッケージには、それに関連するdelegate(エージェント)がある.
// define a closure
def myClosure = {
// call a method that does not exist
append 'Jeff'
append ' was here.'
}
// assign a delegate to the closure
def sb = new StringBuffer()
myClosure.delegate = sb
// execute the closure
myClosure()
assert 'Jeff was here.' == sb.toString()
書き方を変えます.
def closure = {
clear()
set MONTH, JULY
set DATE, 4
set YEAR, 1776
println time
}
def calendar = Calendar.instance
closure.delegate = calendar
closure()
Another bit of info that is missing here is the strategy that a closure uses to decide when to send method calls to the delegate. Each Groovy closure has a resolveStrategy associated with it. This property determines how/if the delegate comes in to play. The 4 possible values for the resolveStrategy are OWNER_FIRST, DELEGATE_FIRST, OWNER_ONLY and DELEGATE_ONLY (all constants defined in groovy.lang.Closure). The default is OWNER_FIRST. Consider the owner to be the "this"wherever the closure is defined. Here is a simple example...
class ResolutionTest {
def append(arg) {
println "you called the append method and passed ${arg}"
}
def doIt() {
def closure = {
append 'Jeff was here.'
}
def buffer = new StringBuffer()
closure.delegate = buffer
// the append method in this ResolutionTest
// will be called because resolveStrategy is
// OWNER_FIRST (the default)
closure()
// give the delegate first crack at method
// calls made inside the closure
closure.resolveStrategy = Closure.DELEGATE_FIRST
// the append method on buffer will
// be called because the delegate gets
// first crack at the call to append()
closure()
}
static void main(String[] a) {
new ResolutionTest().doIt()
}
}
実行結果:
you called the append method and passed Jeff was here.
ソース:
http://java.dzone.com/news/getting-groovy-with-with