MULE 4：REDUCE 方法：如果累加器是对象，Reduce 方法中的元素大小是否有限制？

Question

场景：使用 Mule 4 中的 Reduce 方法将 LIST 缩减为三个参数：

学生名单
教师名单
学生人数

在转换消息中使用以下 Dataweave 代码：

%dw 2.0
output application/java
---
payload reduce((value, acc = { 'totalStudents': 0 as Number,'studentList' : [], 'teachersList' : []}) -> 
    if(
        value.age > 18 and value.age < 25
    ){
        totalStudents : (acc.totalStudents default 0 as Number) + 1,
        studentList : (acc.studentList default [] ) << {
            'studentName' : value.Name ++ " is a Student"
        }
    }else{
        teachersList : acc.teachersList default [] << value.Name ++ " is a Teacher"
    }
)

问题陈述：转换消息已成功处理，但在有效载荷中我只得到两个值：

payload.totalStudents 和
payload.studentList

谁能帮我理解为什么我的结果没有得到 payload.teachersList？

Answer 1

希望这对您有所帮助。由于存在 else 条件，它构建教师列表并忽略学生列表

Answer 2

这也是。在下面的输入中，第二个元素满足 else 条件，因此最终输出仅包含输入中最后 4 个条目的学生。

Answer 3

最后这应该得到你要找的东西：

%dw 2.0
output application/java
---
payload reduce((value, acc = { 'totalStudents': 0 as Number,'studentList' : [], 'teachersList' : []}) -> 
    if(
        value.age > 18 and value.age < 25
    ){
        totalStudents : (acc.totalStudents default 0 as Number) + 1,
        studentList : (acc.studentList default [] ) << {
            'studentName' : value.Name ++ " is a Student"
        },
        teachersList: acc.teachersList
    }else{
         totalStudents : acc.totalStudents,
         studentList : acc.studentList,
        teachersList : (acc.teachersList default [] ) <<  {'teacherName': value.Name ++ " is a Teacher"}
    }
)```

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/fcyNf.png

Answer 4

%dw 2.0
output application/java
---
payload reduce((value, acc = { 'totalStudents': 0 as Number,'studentList' : [], 'teachersList' : []}) -> 
    if(
        value.age > 18 and value.age < 25
    ){
        totalStudents : (acc.totalStudents default 0 as Number) + 1,
        studentList : (acc.studentList default [] ) << {
            'studentName' : value.Name ++ " is a Student"
        },
        teachersList: acc.teachersList
    }else{
        totalStudents : acc.totalStudents,
        studentList : acc.studentList,
        teachersList : (acc.teachersList default [] ) <<  {'teacherName': value.Name ++ " is a Teacher"}
    }
)

MULE 4：REDUCE 方法：如果累加器是对象，Reduce 方法中的元素大小是否有限制？

MULE 4 : REDUCE method : Is there a limit to elements size in Reduce method if the accumulator is an Object?

dataweave

mule4