What is Swift Compiler - Search Paths Import Paths in Xcode 6 Building Settings?

module, swift, xcode6

Solution

Just to share what I have discovered during days of connecting dots. Short answer, Import Search Path `SWIFT_INCLUDE_PATHS` specifies where Swift finds and imports modules.

Modules and Semantic Import

What are modules? Modules improve access to the API of software libraries by replacing the textual preprocessor inclusion model with a more robust, more efficient semantic model. From the user’s perspective, the code looks only slightly different, because one uses an import declaration rather than a #include preprocessor directive like this:

import std.io

It was first announced in Nov 2012 by Apple at LLVM DevMeeting. You can still find the Doug Gregor’s talk here (Video and PDF). At WWDC 2013, Semantic Import was introduced on along with iOS 7, the `@import` was just for it. So it was determinant that module to be part of new language Swift. Documentation of modules can be found here.

Example - How to import

To have a taste, below are steps to create an example app project with HTML Tidy library module.

Create a Swift project (OS X or iOS) in Xcode 6

Create a `module.map` file, and place it in a directory. E.g. `/Users/vladof/module/`

 module tidy [system] {
     header "/usr/include/tidy/tidy.h"
     header "/usr/include/tidy/buffio.h"
     link "tidy"
     export *
 }

Go Build Settings, set `Swift Compiler - Search Paths` > `Import Paths` to the directory that you put the `module.map` file in. `/Users/vladof/module` in my case. Then you can use `import tidy` and leverage useful APIs of HTML Tidy library, even in Swift REPL.

Import

 import tidy

Example code

 var input: CString = "<node>upper case node</node>"
 var tdoc: TidyDoc = tidyCreate() // Initialize "document"
 var rc: Int32 = -1
 var ok = tidyOptSetBool(tdoc, TidyUpperCaseTags, yes) // Convert tags to upper cases
 ok = tidyOptSetBool(tdoc, TidyXmlTags, yes) // Convert to XML

 if ok.value == 1 {
     rc = tidyParseString(tdoc, input) // Parse the input
     if rc >= 0 {
         rc = tidyCleanAndRepair(tdoc) // Tidy it up
     }
     if rc >= 0 {
         rc = tidySaveStdout(tdoc) // Pretty print to console
     }
 }

Print

 <NODE>upper case node</NODE>

Conclude

Also I have experimented with `curl` module. In fact some APIs are not imported as I test, e.g. `curl_easy_setopt()`, let’s hope they catch up in near future. But I am positive this opens a door for Swift developers.

Problem

Original source