数组之间使用字符串的自定义XML元帅

Question

I have a snippet of XML I need to read and write. It's an array of <condition> with an <operator> in between each except for the last entity.

<conditions>                                                                                                                                                                                                                                                                              
    <condition>                                                                                                                                                                                                                                                                           
      <label>a</label>                                                                                                                                                                                                                                                                    
    </condition>                                                                                                                                                                                                                                                                          
    <operator>AND</operator>                                                                                                                                                                                                                                                              
    <condition>                                                                                                                                                                                                                                                                           
      <label>b</label>                                                                                                                                                                                                                                                                    
    </condition>                                                                                                                                                                                                                                                                          
    <operator>AND</operator>                                                                                                                                                                                                                                                              
    <condition>                                                                                                                                                                                                                                                                           
      <label>c</label>                                                                                                                                                                                                                                                                    
    </condition>                                                                                                                                                                                                                                                                          
<conditions>

My Go model looks like this

type Condition struct {                                                                                                                                                                                                                                                                   
    XMLName xml.Name `xml:"condition" json:"-"`                                                                                                                                                                                                                                           
    Label   string   `xml:"label"`                                                                                                                                                                                                                                                        
}                                                                                                                                                                                                                                                                                         

type Conditions struct {                                                                                                                                                                                                                                                                  
    ConditionList []Condition `xml:"condition,omitempty"`                                                                                                                                                                                                                                 
    Operator      string      `xml:"operator"`                                                                                                                                                                                                                                            
}   

If I marshal the struct the operator only appears once on the bottom. as expected

<Conditions>
  <condition>
    <label>a</label>
  </condition>
  <condition>
    <label>b</label>
  </condition>
  <condition>
    <label>c</label>
  </condition>
  <operator>AND</operator>
</Conditions>

How do i get the operator to appear after every condition except for the last one?

The closest i could get was using a wrapper

func (c Conditions) MarshalXML(e *xml.Encoder, start xml.StartElement) error {                                                                                                                                                                                                            

    type tCondition struct {                                                                                                                                                                                                                                                              
        XMLName xml.Name `xml:"condition" json:"-"`                                                                                                                                                                                                                                       
        Label   string   `xml:"label"`                                                                                                                                                                                                                                                    
    }                                                                                                                                                                                                                                                                                     
    type tConditionWithOp struct {                                                                                                                                                                                                                                                        
        XMLName   xml.Name   `xml:"-" json:"-"`                                                                                                                                                                                                                                           
        Condition tCondition `xml: "conditions"`                                                                                                                                                                                                                                          
        Operator  string     `xml:",omitempty"`                                                                                                                                                                                                                                           
    }                                                                                                                                                                                                                                                                                     
    type tWrapper struct {                                                                                                                                                                                                                                                                
        OPS []tConditionWithOp                                                                                                                                                                                                                                                            
    }                                                                                                                                                                                                                                                                                     

    lst := make([]tConditionWithOp, 0, 10)                                                                                                                                                                                                                                                

    for idx, cond := range c.ConditionList {                                                                                                                                                                                                                                              
        tCond := tCondition{                                                                                                                                                                                                                                                              
            Label: cond.Label,                                                                                                                                                                                                                                                            
        }                                                                                                                                                                                                                                                                                 
        tCondOp := tConditionWithOp{                                                                                                                                                                                                                                                      
            Condition: tCond,                                                                                                                                                                                                                                                             
        }                                                                                                                                                                                                                                                                                 

        if idx < len(c.ConditionList)-1 {                                                                                                                                                                                                                                                 
            tCondOp.Operator = c.Operator                                                                                                                                                                                                                                                 
        }                                                                                                                                                                                                                                                                                 

        lst = append(lst, tCondOp)                                                                                                                                                                                                                                                        

    }                                                                                                                                                                                                                                                                                     
    wrapper := tWrapper{                                                                                                                                                                                                                                                                  
        OPS: lst,                                                                                                                                                                                                                                                                         
    }                                                                                                                                                                                                                                                                                     

    return e.EncodeElement(wrapper, start)                                                                                                                                                                                                                                                
}  

But I now have an <OPS> tag

<Conditions>
  <OPS>
    <condition>
      <label>a</label>
    </condition>
    <Operator>AND</Operator>
  </OPS>
  <OPS>
    <condition>
      <label>b</label>
    </condition>
    <Operator>AND</Operator>
  </OPS>
  <OPS>
    <condition>
      <label>c</label>
    </condition>
  </OPS>
</Conditions>

I have created a playground here

https://play.golang.org/p/gagQ3m3EMjY

Answer 1

Interleaving conditions and operator elements into an []interface{} array worked. Thanks

type Operator struct {                                                                                                                                       
    Name string                                                                                                                                              
}                                                                                                                                                            

func (op Operator) MarshalXML(e *xml.Encoder, start xml.StartElement) error {                                                                                
    start.Name.Local = "operator"                                                                                                                            
    return e.EncodeElement(op.Name, start)                                                                                                                   
}                                                                                                                                                            

func (c Conditions) MarshalXML(e *xml.Encoder, start xml.StartElement) error {                                                                               

    start.Name.Local = "conditions"                                                                                                                          
    var arr []interface{}                                                                                                                                    

    for idx, cond := range c.ConditionList {                                                                                                                 
        if idx > 0 {                                                                                                                                         
            arr = append(arr, Operator{Name: c.Operator})                                                                                                    
        }                                                                                                                                                    
        arr = append(arr, cond)                                                                                                                              
    }                                                                                                                                                        

    type root struct {                                                                                                                                       
        ARR []interface{}                                                                                                                                    
    }                                                                                                                                                        

    return e.EncodeElement(root{ARR: arr}, start)                                                                                                            
}