How-tos
This page provides concrete instructions for common scenarios.
- How do I build a Qt-based project?
- How do I make my app build against my library?
- How do I create a module for a third-party library?
- How do I create application bundles and frameworks on iOS, macOS, tvOS, and watchOS?
- How do I apply C/C++ preprocessor macros to only a subset of the files in my product?
How do I build a Qt-based project?
First of all, your project files need to declare a Qt dependency. See Qt Modules for how to do that.
To build the project, you need a matching profile. The following commands set up and use a Qt-specific profile:
$ qbs setup-qt /usr/bin/qmake qt $ cd my_project $ qbs profile:qt
If you plan to use this profile a lot, consider making it the default one:
$ qbs config defaultProfile qt $ cd my_project $ qbs
See Managing Qt Versions for more details.
Note: These instructions are only relevant for building from the command line. If you use Qt Creator, profiles are set up automatically from the information in the Kit.
How do I make my app build against my library?
This is achieved by introducing a dependency between the two products using the Depends item. Here is a simple, but complete example:
import qbs Project { CppApplication { name : "the-app" files : [ "main.cpp" ] Depends { name: "the-lib" } } DynamicLibrary { name: "the-lib" Depends { name: "cpp" } files: [ "lib.cpp", "lib.h", ] Export { Depends { name: "cpp" } cpp.includePaths: [product.sourceDirectory] } } }
The product the-lib
is a dynamic library. It expects other products to build against it, and for that purpose, it exports an include path (via an Export item), so that the source files in these products can include the library's header file.
The product the-app
is an application that expresses its intent to link against the-lib
by declaring a dependency on it. Now main.cpp
can include lib.h
(because of the exported include path) and the application binary will link against the library (because the linker rule in the cpp module considers library dependencies as inputs).
Note: In a non-trivial project, the two products would not be defined in the same file. Instead, you would put them into files of their own and use the Project item's references
property to pull them into the project. The product definitions would stay exactly the same. In particular, their location in the project tree is irrelevant to the relationship between them.
How do I create a module for a third-party library?
If you have pre-built binary files in your source tree, you can create modules for them and then introduce dependencies between your project and the modules to pull in the functionality of a third-party library.
Create the following folder structure to store the module files:
$projectroot/modules/ThirdParty
Then create a file in the directory that specifies the module properties for each supported toolchain. The filename must have the .qbs
extension. The module will be pulled in if a product declares a dependency on it.
In the following example, lib1.dylib
is a multi-architecture library containing both 32-bit and 64-bit code.
---ThirdParty.qbs--- Module { Depends { name: "cpp" } cpp.includePaths: ["/somewhere/include"] Properties { condition: qbs.targetOS.contains("android") cpp.dynamicLibraries: ["/somewhere/android/" + Android.ndk.abi + "/lib1.so"] } Properties { condition: qbs.targetOS.contains("macos") cpp.dynamicLibraries: ["/somewhere/macos/lib1.dylib"] } Properties { condition: qbs.targetOS.contains("windows") && qbs.architecture === "x86" cpp.dynamicLibraries: ["/somewhere/windows_x86/lib1.lib"] } Properties { condition: qbs.targetOS.contains("windows") && qbs.architecture === "x86_64" cpp.dynamicLibraries: ["/somewhere/windows_x86_64/lib1.lib"] } }
Finally, declare dependencies on ThirdParty
in your project:
import qbs CppApplication { name: "the-app" files: ["main.cpp"] Depends { name: "ThirdParty" } }
How do I create application bundles and frameworks on iOS, macOS, tvOS, and watchOS?
Creating an application bundle or framework is achieved by introducing a dependency on the Bundle module and setting the bundle.isBundle
property to true
.
Here is a simple example for an application:
import qbs Application { Depends { name: "cpp" } Depends { name: "bundle" } bundle.isBundle: true name: "the-app" files: ["main.cpp"] }
and for a framework:
import qbs DynamicLibrary { Depends { name: "cpp" } Depends { name: "bundle" } bundle.isBundle: true name: "the-lib" files: ["lib.cpp", "lib.h"] }
Qbs also supports building static frameworks - you can create one by replacing DynamicLibrary
with StaticLibrary
in the example above.
Note: When using the Application
or Library
templates (or derived templates like CppApplication
, DynamicLibrary
, and StaticLibrary
), your products will build as bundles on Apple platforms by default (this behavior is subject to change in a future release).
To explicitly control whether your product is built as a bundle, set the bundle.isBundle
property. Setting the consoleApplication
property of your product will also influence whether your product is built as a bundle.
Building your application against your framework is the same as linking a normal dynamic or static library; see the How do I make my app build against my library? section for an example.
How do I apply C/C++ preprocessor macros to only a subset of the files in my product?
Use a Group item to define a subset of project files. To add macros within the group, you need to use the outer.concat
property, because you are adding macros to those specified in the outer scope.
In the following example, MACRO_EVERYWHERE
is defined for all files in the Product unless a Group
overrides the macro, whereas MACRO_GROUP
is only defined for groupFile.cpp
.
Product { Depends { name: "cpp" } cpp.defines: ["MACRO_EVERYWHERE"] Group { cpp.defines: outer.concat("MACRO_GROUP") files: "groupFile.cpp" } }
The cpp.defines
statements inside a Group
only apply to the files in that Group
, and therefore you cannot use a Group
to include a bunch of files and globally visible macros. The macros must be specified in a Properties item at the same level as the Group
if they need to be visible to files outside the Group
:
Product { Depends { name: "cpp" } Group { condition: project.supportMyFeature files: "myFile.cpp" } property stringList commonDefines: ["ONE", "TWO"] Properties { condition: project.supportMyFeature cpp.defines: commonDefines.concat("MYFEATURE_SUPPORTED") } }