Answer: Xcode File Templates are blueprint files and metadata plists stored in ~/Library/Developer/Xcode/Templates/File Templates/ that allow generating multiple pre-wired Swift files with automatic text and identifier substitution in a single step.

Xcode locates custom templates inside your home directory:

~/Library/Developer/Xcode/Templates/
└── File Templates/
    └── <Section Name>/
        └── <TemplateName>.xctemplate/
            ├── TemplateInfo.plist
            └── ___FILEBASENAME___*.swift

Key Components

1. Folder Hierarchy:

   • File Templates: Mandatory folder name required by Xcode.
   • <Section Name>: The category group displayed in Xcode's template picker (e.g., UIKit, SwiftUI, Architecture).
   • <TemplateName>.xctemplate: The template package folder. Must have the .xctemplate extension.

2. The Two Placeholder Rules:

   • ___FILEBASENAME___ in file names: Expands to the output file's own name without extension (e.g., ___FILEBASENAME___Presenter.swift -> ProfilePresenter.swift).
   • ___VARIABLE_productName:identifier___ in file contents: Expands to the value entered in the template option dialog sanitized as a valid Swift identifier (e.g. Profile).
   • Never use ___FILEBASENAME___ inside file contents for multi-file templates, or it will generate doubled names like ProfilePresenterPresenter.

3. TemplateInfo.plist Configuration:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Kind</key>
    <string>Xcode.IDEFoundation.TextSubstitutionFileTemplateKind</string>
    <key>Identifier</key>
    <string>com.template.ArchitectureFeature</string>
    <key>Name</key>
    <string>Architecture Feature</string>
    <key>Description</key>
    <string>Generates multi-file architecture components.</string>
    <key>Summary</key>
    <string>Architecture Feature Template</string>
    <key>SortOrder</key>
    <string>1</string>
    <key>Platforms</key>
    <array>
        <string>com.apple.platform.iphoneos</string>
    </array>
    <key>Options</key>
    <array>
        <dict>
            <key>Identifier</key><string>productName</string>
            <key>Name</key><string>Feature Name:</string>
            <key>Description</key><string>Base name of the feature (e.g. Profile)</string>
            <key>Type</key><string>text</string>
            <key>Required</key><true/>
            <key>NotPersisted</key><true/>
        </dict>
    </array>
</dict>
</plist>

Full Placeholder Reference

Placeholder	Expands To	Usage Scope
___FILEBASENAME___	The generated file's own name (without .swift)	Blueprint file names
___VARIABLE_productName:identifier___	The sanitized Swift identifier from the dialog prompt	Blueprint file contents
___FILENAME___	Full output filename with extension	Header comments
___PACKAGENAME___	Xcode target or package name	Header comments
___FULLUSERNAME___	macOS account full name	Header comments
___DATE___	Today's date (short format)	Header comments
___COPYRIGHT___	Project copyright header	Header comments

Using Custom Templates in Xcode

1. Select the destination group in Xcode's Project navigator.
2. Select File ▸ New ▸ File from Template… (Note: File ▸ New ▸ File only shows built-in templates).
3. Scroll to the bottom to find your custom category section.
4. Enter the feature name (e.g., Profile), click Next, enter the matching name in Save As, select the target membership, and click Create.

Troubleshooting & Diagnostics

• Template does not appear: Ensure TemplateInfo.plist is valid (plutil -lint TemplateInfo.plist). Xcode must be fully quit (⌘Q) and restarted because templates load once at launch.
• Empty type names in files: Ensure TemplateInfo.plist includes the Options block declaring productName.
• Doubled type names: Replace ___FILEBASENAME___ inside file contents with ___VARIABLE_productName:identifier___.