英文:
How can I get a variable already defined in drools lhs?
问题
我使用 drools API 来定义一个规则，如下所示：
PackageDescr pkg = DescrFactory.newPackage()
.name("org.drools.example")
.newRule().name("Xyz")
.attribute("ruleflow-grou","bla")
.lhs()
.and()
.pattern("Student").id("$stu", false ).constraint("name==miko").constraint("age > 6").end()
.not().pattern("Bar").constraint("a+b==c").end().end()
.end()
.end()
最终它将转化为一个 DRL 文件，如下所示：
$stu: Student(name == miko, age > 6)
not Bar(a + b == c)
我的问题是，如果我想要获取之前定义的 `$stu` 变量，并添加一些额外的约束条件，比如：
```$stu(grade != 2)```
我该如何获取并重用它呢？
英文:
I'm using drools api to define a rule like this:
PackageDescr pkg = DescrFactory.newPackage()
.name("org.drools.example")
.newRule().name("Xyz")
.attribute("ruleflow-grou","bla")
.lhs()
.and()
.pattern("Student").id( "$stu", false ).constraint("name==miko").constraint("age > 6").end()
.not().pattern("Bar").constraint("a+b==c").end().end()
.end()
.end()
Finnally it will transfer into drl file like:
$stu: Studeng(name == miko, age > 6)
not Bar(a + b == c)
My question is if I wanna to get the '$stu' variable defined befor and to add some more constaints, like:
$stu(grade != 2)
how can I get it and reuse it?
答案1
得分: 0
为了向Student添加额外的约束条件，只需在你已经拥有的约束条件后面链接它。
.pattern("Student")
.id( "$stu", false )
.constraint("name == "miko"")
.constraint("age > 6")
.constraint("grade != 2 ")
.end()
这将生成:
$stu: Student( name == "miko", age > 6, grade != 2)
（我假设这是你想要做的，因为`$stu( grade != 2 )`不是有效的语法。）
此规则将识别任何名字为“miko”的学生（请注意这是区分大小写的！），年龄大于6，并且成绩不等于2。
英文:
To add an additional constraint to Student, just chain it after the constraints you already have.
.pattern("Student")
.id( "$stu", false )
.constraint("name == \"miko\"")
.constraint("age > 6")
.constraint("grade != 2 ")
.end()
Which would generate:
$stu: Student( name == "miko", age > 6, grade != 2)
(I'm presuming that's what you're trying to do, because $stu( grade != 2 ) is not valid syntax.)
This rule would identify any students with the name "miko" (note this is case sensitive!), have an age greater than 6, and a grade not equal to 2.
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