for component: v0.22.0+ A component for iteration. Used for iterating over arrays, slices, and structs, as well as for repeatedly executing a chain or sub-rule chain starting from a specified node.

Configuration

Field	Type	Description	Default Value
range	string	The target expression for iteration	1..3
do	string	Specifies the node or sub-rule chain for processing the iterated elements	s3
mode	int	Mode of merging iteration results, 0 - Ignore, 1 - Append, 2 - Override, 3- Asynchronous execution	0

range

• Supports iterating over arrays, slices, and structs. For example: ${msg.items} iterates over msg.items,1..5 iterates over []int{1,2,3,4,5}
• If empty, iterates over the entire msg
• Access the message body through the ${msg} variable; if the message's dataType is JSON, you can access the fields of msg by ${msg.XX}. For example: ${msg.items}
• Access message metadata through the ${metadata} variable. For example ${metadata.customerName}
• Access message type through the ${msgType} variable
• Access data type through the ${dataType} variable

Expression examples:

• ${msg.items} iterates over msg.items
• 1..3 iterates over []int{1,2,3}, with do executed 3 times

For more expr expression syntax, refer to: expr (opens new window)

do

• For example: "s1", item will start executing from the branch chain of s1, until the chain is completed, then return to the starting point of iteration
• An item can also be processed by a sub-rule chain, usage: chain:chainId, for example: chain:rule01, item will start executing from the sub-chain rule01, until the chain is completed, then return to the starting point of iteration

TIP

• Access the current iteration index through ${metadata._loopIndex}
• Access the current iterated item through ${metadata._loopItem}
• Access the current iterated key through ${metadata._loopKey}, which only has a value when iterating over a struct
• If the loop object is of type []interface{}, the value of the item will be passed to the processing node through msg.Data

Relation Type

• Success: If executed successfully, sends the message to the Success chain
• Failure: If execution fails, sends the message to the Failure chain

Execution Result

• If sync=true, merge each iteration result and pass it to the next node; otherwise, do not modify msg.Data.
• msg.metadata: Will be modified by the iteration component.

Configuration Example

{
  "id": "s1",
  "type": "for",
  "name": "Iteration",
  "configuration": {
    "range": "${msg.items}",
    "do":        "s3"
  }
}

Related Documentation

• Component Configuration Variables