# ANTLR4 Language Target, Runtime for Swift

## Performance Note

To use ANTLR4 Swift target in production environment, make sure to turn on compiler optimizations by following [these instructions](https://github.com/apple/swift-package-manager/blob/master/Documentation/Usage.md#build-configurations) if you use SwiftPM to build your project. If you are using Xcode to build your project, it's unlikely you will not use `release` build for production build.

Conclusion is, you need to turn on `release` mode (which will have all the optimization pre configured for you) so the ANTLR4 Swift target can have reasonable parsing speed.


## Install ANTLR4

Make sure you have the ANTLR
installed. [The getting started guide](getting-started.md) should get
you started.

## Create a Swift lexer or parser 
This is pretty much the same as creating a Java lexer or parser, 
except you need to specify the language target, for example:

``` 
$ antlr4 -Dlanguage=Swift MyGrammar.g4 
``` 
For a full list of antlr4 tool options, please visit the
[tool documentation page](tool-options.md).


## Build your Swift project with ANTLR runtime

The following instructions assume Xcode as the IDE.

Note that even if you are otherwise using ANTLR from a binary distribution,
you should compile the ANTLR Swift runtime from source, because the Swift
language does not yet have a stable ABI.

ANTLR uses Swift Package Manager to generate Xcode project files. Note that
Swift Package Manager does not currently support iOS, watchOS, or tvOS, so
if you wish to use those platforms, you will need to alter the project build
settings manually as appropriate.

### Download source code for ANTLR

```
git clone https://github.com/antlr/antlr4
```

### Generate Xcode project for ANTLR runtime

The `boot.py` script includes a wrapper around `swift package
generate-xcodeproj`. Use this to generate `Antlr4.xcodeproj` for the ANTLR
Swift runtime.

```
cd antlr4/runtime/Swift
python boot.py --gen-xcodeproj
```

### Import ANTLR Swift runtime into your project

Open your own project in Xcode.

Open Finder in the `runtime/Swift` directory:

```
# From antlr4/runtime/Swift
open .
```

Drag `Antlr4.xcodeproj` into your project.

After this is done, your Xcode project navigator will be something like the
screenshot below. In this example, your own project is "Smalltalk", and you
will be able to see `Antlr4.xcodeproj` shown as a contained project.

<img src=images/xcodenav.png width="300">

### Edit the build settings if necessary

Swift Package Manager currently does not support iOS, watchOS, or tvOS.  If
you wish to build for those platforms, you will need to alter the project
build settings manually.

### Add generated parser and lexer to project

Make sure the parsers/lexers
generated in __step 2__ are added to the project. To do this, you can
drag the generated files from Finder to the Xcode IDE. Remember to
check __Copy items if needed__ to make sure the files are actually
moved into the project folder instead of symbolic links (see the
screenshot below). After moving you will be able to see your files in
the project navigator.  Make sure that the Target Membership settings
are correct for your project.

<img src=images/dragfile.png width="500">

### Add the ANTLR Swift runtime as a dependency

Select your own project in Xcode and go to the Build Phases settings panel.
Add the ANTLR runtime under __Target Dependencies__ and __Link Binary With
Libraries__.

<img src=images/xcodedep.png width="800">

### Build your project

The runtime and generated grammar should now build correctly.