Reusing Other Libraries

Many of our examples link with various libraries that we have supplied. The one we use most frequently is called libutils. You can download a tarball containing this library here.[1] Create a shell/environment variable CPPLIBS that points to a convenient (empty) directory and then unpack the utils tarball in that directory.


When we set up projects that reuse utils we will always assume that the shell/environment variable $CPPLIBS (or %CPPLIBS% in Windows) has been properly set to contain the "libs root." This variable is used for two purposes: It is the parent directory of all the C++ source code for libraries supplied by us (or by you), and it is also the destination directory of the compiled shared object code for those libraries.

qmake can access an environment variable such as CPPLIBS from inside a project file using the syntax $$(CPPLIBS).qmake can also include other project file (fragments). For example, the project file in Example 7.1 includes a .pri file located in a directory relative to your environment variable CPPLIBS.

Example 7.1. src/qapp-gui/

include ($$(CPPLIBS)/utils/common.pri)

# Input
HEADERS += messager.h
SOURCES += main.cpp messager.cpp

The command

qmake -project

produces a project file that contains information based on the contents of the current working directory. In particular, qmake cannot know about external libraries that you may need to build your project. So, if your project depends on an external library, you must edit the project file and add assignments to three of the variables.

For example, suppose we are developing an application that uses our utils library. The header files are located in $CPPLIBS/utils and the lib shared object files are located in $CPPLIBS. Then we must add the following lines to the project file

INCLUDEPATH += $$(CPPLIBS)/utils # the source header files
LIBS += -L$$(CPPLIBS) # add this to the lib search path
LIBS += -lutils # link with

Assignments to the LIBS variable generally contain two kinds of linker switches that are passed directly to the compiler and the linker. For more information about what the linker switches mean see Section C.2.

Part I: Introduction to C++ and Qt 4

C++ Introduction


Introduction to Qt



Inheritance and Polymorphism

Part II: Higher-Level Programming


Introduction to Design Patterns


Generics and Containers

Qt GUI Widgets


Validation and Regular Expressions

Parsing XML

Meta Objects, Properties, and Reflective Programming

More Design Patterns

Models and Views

Qt SQL Classes

Part III: C++ Language Reference

Types and Expressions

Scope and Storage Class

Statements and Control Structures

Memory Access

Chapter Summary

Inheritance in Detail

Miscellaneous Topics

Part IV: Programming Assignments

MP3 Jukebox Assignments

Part V: Appendices

MP3 Jukebox Assignments


MP3 Jukebox Assignments

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An Introduction to Design Patterns in C++ with Qt 4
An Introduction to Design Patterns in C++ with Qt 4
ISBN: 0131879057
EAN: 2147483647
Year: 2004
Pages: 268
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