这是新的《CloudFormation 模板参考指南》**。请更新您的书签和链接。有关开始使用 CloudFormation 的帮助，请参阅《AWS CloudFormation 用户指南》[https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/Welcome.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/Welcome.html)。

# `Conditions` 部分中的 `Fn::ForEach` 示例
<a name="intrinsic-function-reference-foreach-example-conditions"></a>

这些示例演示了如何使用 `Conditions` 部分中的 `Fn::ForEach` 内置函数。有关此部分的更多信息，请参阅《AWS CloudFormation 用户指南》**中的 [Conditions](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/conditions-section-structure.html)。

**重要**  
`Conditions` 必须是列出的第二个属性或更高属性。如果 `Conditions` 是 `Fn::ForEach` 的模板片段参数中列出的第一个属性，则堆栈创建将失败。

```
Resources:
  'Fn::ForEach::Topics':
    - LogicalId
    - !Ref TopicList
    - '${LogicalId}':
        Condition: !Sub 'TopicCondition${LogicalId}'
        Type: AWS::SNS::Topic
        Properties:
          TopicName: !Sub 'My${LogicalId}'
```

`Conditions` 必须作为第二个密钥或更高密钥添加，创建堆栈才能成功：

```
Resources:
  'Fn::ForEach::Topics':
    - LogicalId
    - !Ref TopicList
    - '${LogicalId}':
        Type: AWS::SNS::Topic
        Condition: !Sub 'TopicCondition${LogicalId}'
        Properties:
          TopicName: !Sub 'My${LogicalId}'
```

**Topics**
+ [复制单个条件](#intrinsic-function-reference-foreach-example-replicated-single-condition)

## 复制单个条件
<a name="intrinsic-function-reference-foreach-example-replicated-single-condition"></a>

此示例使用 `Conditions` 部分中的 `Fn::ForEach` 内置函数来复制具有不同属性的多个相似条件。

### JSON
<a name="intrinsic-function-reference-foreach-example-conditions.json"></a>

```
{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Parameters": {
        "ParamA": {
            "Type": "String",
            "AllowedValues": [
                "true",
                "false"
            ]
        },
        "ParamB": {
            "Type": "String",
            "AllowedValues": [
                "true",
                "false"
            ]
        },
        "ParamC": {
            "Type": "String",
            "AllowedValues": [
                "true",
                "false"
            ]
        },
        "ParamD": {
            "Type": "String",
            "AllowedValues": [
                "true",
                "false"
            ]
        }
    },
    "Conditions": {
        "Fn::ForEach::CheckTrue": [
            "Identifier",
            ["A", "B", "C", "D"],
            {
                "IsParam${Identifier}Enabled": {
                    "Fn::Equals": [
                        {"Ref": {"Fn::Sub": "Param${Identifier}"}},
                        "true"
                    ]
                }
            }
        ]
    },
    "Resources": {
        "WaitConditionHandle": {
            "Type": "AWS::CloudFormation::WaitConditionHandle"
        }
    }
}
```

### YAML
<a name="intrinsic-function-reference-foreach-example-conditions.yaml"></a>

```
AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Parameters:
  ParamA:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
  ParamB:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
  ParamC:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
  ParamD:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
Conditions:
  'Fn::ForEach::CheckTrue':
    - Identifier
    - [A, B, C, D]
    - 'IsParam${Identifier}Enabled': !Equals 
        - !Ref 
          'Fn::Sub': 'Param${Identifier}'
        - 'true'
Resources:
  WaitConditionHandle:
    Type: AWS::CloudFormation::WaitConditionHandle
```

转换后的模板将等同于以下模板：

```
AWSTemplateFormatVersion: 2010-09-09
Parameters:
  ParamA:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
  ParamB:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
  ParamC:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
  ParamD:
    Type: String
    AllowedValues:
      - 'true'
      - 'false'
Conditions:
  IsParamAEnabled: !Equals 
    - !Ref ParamA
    - 'true'
  IsParamBEnabled: !Equals 
    - !Ref ParamB
    - 'true'
  IsParamCEnabled: !Equals 
    - !Ref ParamC
    - 'true'
  IsParamDEnabled: !Equals 
    - !Ref ParamD
    - 'true'
Resources:
  WaitConditionHandle:
    Type: AWS::CloudFormation::WaitConditionHandle
```