#Alibaba Cloud - Variables

The Serverless framework provides a powerful variable system which allows you to add dynamic data into your serverless.yml. With Serverless Variables, you'll be able to do the following:

• Reference & load variables from environment variables
• Reference & load variables from CLI options
• Recursively reference properties of any type from the same serverless.yml file
• Recursively reference properties of any type from other YAML / JSON files
• Recursively nest variable references within each other for ultimate flexibility
• Combine multiple variable references to overwrite each other

Note: You can only use variables in serverless.yml property values, not property keys. So you can't use variables to generate dynamic logical IDs in the custom resources section for example.

#Reference variables from environment variables

To reference variables from environment variables, use the ${env:someProperty} syntax in your serverless.yml.

service: new-service

provider:
  name: aliyun
  runtime: nodejs8
  credentials: ~/.aliyuncli/credentials # path must be absolute

plugins:
  - serverless-aliyun-function-compute

functions:
  ossTriggerTest:
    handler: index.ossTriggerHandler
    events:
      - oss:
          sourceArn: acs:oss:cn-shanghai:${env:ALIYUN_ACCOUNT}:my-service-resource
          triggerConfig:
            events:
              - oss:ObjectCreated:PostObject
              - oss:ObjectCreated:PutObject
            filter:
              key:
                prefix: source/

#Reference Properties In serverless.yml

To self-reference properties in serverless.yml, use the ${self:someProperty} syntax in your serverless.yml. This functionality is recursive, so you can go as deep in the object tree as you want.

service: new-service

provider:
  name: aliyun
  runtime: nodejs8
  credentials: ~/.aliyuncli/credentials # path must be absolute

plugins:
  - serverless-aliyun-function-compute

functions:
  first:
    handler: index.first
    events:
      - http:
          path: ${self:custom.path}
          method: get

  second:
    handler: index.second
    events:
      - http:
          path: ${self:custom.path}
          method: post

In the above example you're setting a global event resource for all functions by referencing the resource property in the same serverless.yml file. This way, you can easily change the event resource for all functions whenever you like.

#Reference Variables in JavaScript Files

To add dynamic data into your variables, reference javascript files by putting ${file(../myFile.js):someModule} syntax in your serverless.yml. Here's an example:

// myCustomFile.js
module.exports.path = () => {
  // Code that generates dynamic data
  return '/quo/foo/bar';
};

# serverless.yml
service: new-service

provider:
  name: aliyun
  runtime: nodejs8
  credentials: ~/.aliyuncli/credentials # path must be absolute

plugins:
  - serverless-aliyun-function-compute

functions:
  first:
    handler: index.first
    events:
      - http:
          path: ${file(../myCustomFile.js):path} # Reference a specific module
          method: get

You can also return an object and reference a specific property. Just make sure you are returning a valid object and referencing a valid property:

// myCustomFile.js
module.exports.paths = () => {
  // Code that generates dynamic data
  return {
    current: '/quo/foo/bar',
  };
};

# serverless.yml
service: new-service

provider:
  name: aliyun
  runtime: nodejs8
  credentials: ~/.aliyuncli/credentials # path must be absolute

plugins:
  - serverless-aliyun-function-compute

functions:
  first:
    handler: index.first
    events:
      - http:
          path: ${file(../myCustomFile.js):paths.current} # Reference a specific module
          method: get

#Multiple Configuration Files

Adding many custom resources to your serverless.yml file could bloat the whole file, so you can use the Serverless Variable syntax to split this up.

resources:
  Resources: ${file(aliyun-cloud-resources.json)}

The corresponding resources which are defined inside the aliyun-cloud-resources.json file will be resolved and loaded into the Resources section.