For loops example (#15)

Basic vnet / subnet demo example.

Author: riosengineer

bicep-examples/loops/README.md

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+# Azure Bicep - Iterative loops (for)
+
+## Introduction
+
+For loops in Azure Bicep can be a great way to simplify and minimise your Bicep templates, as they allow you to define multiple copies of a resource which helps reduce and avoids us repeating code in our Bicep templates. 
+
+Using a for loop, you can quickly deploy multiple resources, in this instance a virtual network resource with multiple subnets in one block. 
+
+You can go through the Microsoft Learn training module for this which is great [here](https://learn.microsoft.com/en-us/training/modules/build-flexible-bicep-templates-conditions-loops/).
+
+## 📃 Benefits of using for loops in Bicep
+
+1. ✅ DRY (Don't repeat yourself) - avoids repeating Bicep code uncessarily
+
+2. ✅ Clean templates. By avoiding duplicating code, we can reduce large template files with lots of code lines
+
+3. ✅ Best practice. It's good practice to use for loops in your Bicep templates for the reasons above as well as maintainability as you scale
+
+## For Loop Example
+
+In the basic example within the `main.bicep` file, we can using the `for` property to state for each `vnet` resource, loop through and create the virtual network with subnets.
+
+As the variable (refer to the `main.bicep` file) also contains the required subnets, we're further looping the sub-property within the `vnet` to loop for each `subnet` within the `vnet` as it deploys.
+
+```javascript
+resource vnet 'Microsoft.Network/virtualNetworks@2020-06-01' = [for vnet in vnets: {
+  name: vnet.name
+  location: location
+  properties: {
+    addressSpace: {
+      addressPrefixes: [
+        vnet.addressPrefix
+      ]
+    }
+    subnets: [for subnet in vnet.subnets: {
+      name: subnet.name
+      properties: {
+        addressPrefix: subnet.subnetPrefix
+      }
+    }]
+  }
+}]
+```
+
+## 🚀 Deployment
+
+> [!NOTE]  
+> You need to have a resource group deployed before trying this out.
+
+In VisualStudio Code open a terminal and run:
+
+CLI
+
+```bash
+az login
+az account set --subscription 'subscription name or id'
+az deployment group create -g 'your-rg' --confirm-with-what-if -f '.\main.bicep'
+```
+
+or PowerShell
+
+```powershell
+Connect-AzAccount
+Set-AzContext -Subscription "subscription name or id"
+New-AzResourceGroupDeployment -Confirm -ResourceGroup "your-rg -TemplateFile "main.bicep"
+```

bicep-examples/loops/main.bicep

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+targetScope = 'resourceGroup'
+
+metadata name = 'Virtual Network with Subnet loop'
+metadata description = 'Showcasing Azure Bicep iterative loops - basic example'
+metadata owner = 'networks@example.com'
+
+@description('Azure region for deployments chosen from the resource group.')
+param location string = resourceGroup().location
+
+@description('The Virtual Network and subnet address spaces & names.')
+var vnets = [
+  {
+    name: 'vnet-uks-bicepify-dev'
+    addressPrefix: '10.0.0.0/21'
+    subnets: [
+      {
+        name: 'sql'
+        subnetPrefix: '10.0.1.0/24'
+      }
+      {
+        name: 'backend'
+        subnetPrefix: '10.0.2.0/24'
+      }
+      {
+        name: 'app-service'
+        subnetPrefix: '10.0.3.0/26'
+      }
+    ]
+  }
+]
+
+// Virtual Network with subnet loop
+resource vnet 'Microsoft.Network/virtualNetworks@2020-06-01' = [for vnet in vnets: {
+  name: vnet.name
+  location: location
+  properties: {
+    addressSpace: {
+      addressPrefixes: [
+        vnet.addressPrefix
+      ]
+    }
+    subnets: [for subnet in vnet.subnets: {
+      name: subnet.name
+      properties: {
+        addressPrefix: subnet.subnetPrefix
+      }
+    }]
+  }
+}]