为提高灵活性，可以在 Cloud Assembly 中向云模板代码添加表达式。

表达式的工作原理

Cloud Assembly 表达式使用 ${expression} 构造，如以下示例中所示。

注： Cloud Assembly 表达式与正则表达式不同。请参见 Cloud Assembly 的 表达式语法。

以下代码示例已经过修剪，仅显示重要行。未经编辑的整个云模板显示在最后。

示例

在部署时，允许用户粘贴在远程访问所需的加密密钥中： 

inputs:
  sshKey:
    type: string
    maxLength: 500
resources:
  frontend:
    type: Cloud.Machine
    properties:
      remoteAccess:
        authentication: publicPrivateKey
        sshKey: '${input.sshKey}'

要部署到 VMware Cloud on AWS，请将文件夹名称设置为所需的 Workload 名称： 

inputs:
  environment:
    type: string
    enum:
      - AWS
      - vSphere
      - Azure
      - VMC
      - GCP
    default: vSphere
resources:
  frontend:
    type: Cloud.Machine
    properties:
      folderName: '${input.environment == "VMC" ? "Workload" : ""}'

部署时，使用与所选环境匹配的全小写 env 标记对计算机进行标记： 

inputs:
  environment:
    type: string
    enum:
      - AWS
      - vSphere
      - Azure
      - VMC
      - GCP
    default: vSphere
resources:
  frontend:
    type: Cloud.Machine
    properties:
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'

将前端集群中的计算机数设置为 1（小型）或 2（大型）。请注意，大型集群是通过清除过程设置的： 

inputs:
  envsize:
    type: string
    enum:
      - Small
      - Large
resources:
  frontend:
    type: Cloud.Machine
    properties:
      count: '${input.envsize == "Small" ? 1 : 2}'

通过绑定到在网络资源中找到的属性，将计算机连接到同一 Default 网络： 

resources:
  frontend:
    type: Cloud.Machine
    properties:
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  apitier:
    type: Cloud.Machine
    properties:
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  Cloud_Network_1:
    type: Cloud.Network
    properties:
      name: Default
      networkType: existing

对提交到 API 的访问凭据进行加密： 

resources:
  apitier:
    type: Cloud.Machine
    properties:
      cloudConfig: |
        #cloud-config
        runcmd:
          - export apikey=${base64_encode(input.username:input.password)}
          - curl -i -H 'Accept:application/json' -H 'Authorization:Basic :$apikey' http://example.com

发现 API 计算机的地址： 

resources:
  frontend:
    type: Cloud.Machine
    properties:
      cloudConfig: |
        runcmd:
          - echo ${resource.apitier.networks[0].address}
  apitier:
    type: Cloud.Machine
    properties:
      networks:
        - network: '${resource.Cloud_Network_1.name}'

完整云模板

inputs:
  environment:
    type: string
    enum:
      - AWS
      - vSphere
      - Azure
      - VMC
      - GCP
    default: vSphere
  sshKey:
    type: string
    maxLength: 500
  envsize:
    type: string
    enum:
      - Small
      - Large
resources:
  frontend:
    type: Cloud.Machine
    properties:
      folderName: '${input.environment == "VMC" ? "Workload" : ""}'
      image: ubuntu
      flavor: medium
      count: '${input.envsize == "Small" ? 1 : 2}'
      remoteAccess:
        authentication: publicPrivateKey
        sshKey: '${input.sshKey}'
      cloudConfig: |
        packages:
          - nginx
        runcmd:
          - echo ${resource.apitier.networks[0].address}
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  apitier:
    type: Cloud.Machine
    properties:
      folderName: '${input.environment == "VMC" ? "Workload" : ""}'
      image: ubuntu
      flavor: small
      cloudConfig: |
        #cloud-config
        runcmd:
          - export apikey=${base64_encode(input.username:input.password)}
          - curl -i -H 'Accept:application/json' -H 'Authorization:Basic :$apikey' http://example.com
      remoteAccess:
        authentication: publicPrivateKey
        sshKey: '${input.sshKey}'
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  Cloud_Network_1:
    type: Cloud.Network
    properties:
      name: Default
      networkType: existing
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'

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