Fn::MergeMapToList merges multiple source mappings into a list of mappings, combining values by position.
Declaration
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JSON
{ "Fn::MergeMapToList": [ { "key_1": ["key_1_item_1", "key_1_item_2", ...] }, { "key_2": ["key_2_item_1", "key_2_item_2", ...], }, ... ] } -
YAML
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Syntax for the full function name:
Fn::MergeMapToList: - key_1: - key_1_item_1 - key_1_item_2 - ... - key_2: - key_2_item_1 - key_2_item_2 - ... - ... -
Syntax for the short form:
!MergeMapToList [{key_1: [key_1_item_1, key_1_item_2, ..]}, {key_2: [key_2_item_1, key_2_item_2, ...]}, ...]
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Parameters
[{key_1: [key_1_item_1, key_1_item_2, ..]}, {key_2: [key_2_item_1, key_2_item_2, ...]},...]: the source mappings. Each source mapping must have a list of values.
The merge follows these rules:
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The key and the first value in each source mapping are merged into the first mapping in the list.
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The key and the second value are merged into the second mapping, and so on for subsequent values.
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The resulting list length equals the largest value count among all source mappings. If source mappings have different numbers of values, the last value of a shorter mapping is repeated to fill the remaining positions.
Return value
The list of merged mappings.
Syntax examples
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Three source mappings with the same number of values:
Fn::MergeMapToList: - key_1: - key_1_item_1 - key_1_item_2 - key_2: - key_2_item_1 - key_2_item_2 - key_3: - key_3_item_1 - key_3_item_2Result:
- key_1: key_1_item_1 key_2: key_2_item_1 key_3: key_3_item_1 - key_1: key_1_item_2 key_2: key_2_item_2 key_3: key_3_item_2 -
Three source mappings with different numbers of values:
Fn::MergeMapToList: - key_1: - key_1_item_1 - key_1_item_2 - key_2: - key_2_item_1 - key_2_item_2 - key_2_item_3 - key_3: - key_3_item_1 - key_3_item_2Result:
- key_1: key_1_item_1 key_2: key_2_item_1 key_3: key_3_item_1 - key_1: key_1_item_2 key_2: key_2_item_2 key_3: key_3_item_2 - key_1: key_1_item_2 key_2: key_2_item_3 key_3: key_3_item_2
Usage example
The following template adds all instances created by WebServer to the server group of a Server Load Balancer (SLB) instance:
ROSTemplateFormatVersion: '2015-09-01'
Resources:
WebServer:
Type: ALIYUN::ECS::InstanceGroupClone
Properties:
SourceInstanceId: i-xxxxx
Password: Hello****
MinAmount: 1
MaxAmount: 1
CreateVServerGroup:
Type: ALIYUN::SLB::VServerGroup
Properties:
LoadBalancerId: lb-****
VServerGroupName: VServerGroup-****
BackendServers:
!MergeMapToList
- Port:
- 6666
- 9090
- 8080
- ServerId: !GetAtt WebServer.InstanceIds
- Weight:
- 20
- 100