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ConfigBase class defines the basic interface of all config classes. It can not be used by itself (it is an abstract base class) and you will always use one of its derivations: FileConfig, RegConfig or any other.

However, usually you don’t even need to know the precise nature of the class you’re working with but you would just use the ConfigBase methods. This allows you to write the same code regardless of whether you’re working with the registry under Win32 or text-based config files under Unix (or even Windows 3.1 .INI files if you’re really unlucky). To make writing the portable code even easier, Widgets provides a typedef Config which is mapped onto the native ConfigBase implementation on the given platform: i.e. RegConfig under Win32 and FileConfig otherwise.

See config overview for the descriptions of all features of this class.

It is highly recommended to use static functions Get() and/or Set(), so please have a look at them.

Derived from

No base class


Here is how you would typically use this class:

// using Config instead of writing FileConfig or RegConfig enhances
// portability of the code
Config config = new Config("MyAppName");
String str;
if ( config->Read("LastPrompt", &str) ) {
  // last prompt was found in the config file/registry and its value is now
  // in str
else {
  // no last prompt...
// another example: using default values and the full path instead of just
// key name: if the key is not found , the value 17 is returned
long value = config->Read("/LastRun/CalculatedValues/MaxValue", 17);
// at the end of the program we would save everything back
config->Write("LastPrompt", str);
config->Write("/LastRun/CalculatedValues/MaxValue", value);
// the changes will be written back automatically
delete config;

This basic example, of course, doesn’t show all Config features, such as enumerating, testing for existence and deleting the entries and groups of entries in the config file, its abilities to automatically store the default values or expand the environment variables on the fly. However, the main idea is that using this class is easy and that it should normally do what you expect it to.

NB: in the documentation of this class, the words “config file” also mean “registry hive” for RegConfig and, generally speaking, might mean any physical storage where a ConfigBase-derived class stores its data.

Function groups

Static functions

These functions deal with the “default” config object. Although its usage is not at all mandatory it may be convenient to use a global config object instead of creating and deleting the local config objects each time you need one (especially because creating a FileConfig object might be a time consuming operation). In this case, you may create this global config object in the very start of the program and Set() it as the default. Then, from anywhere in your program, you may access it using the Get() function. Note that you must delete this object (usually in App#on_exit) in order to avoid memory leaks, Widgets won’t do it automatically.

As it happens, you may even further simplify the procedure described above: you may forget about calling Set(). When Get() is called and there is no current object, it will create one using Create() function. To disable this behaviour DontCreateOnDemand() is provided.

Note:* You should use either Set() or Get() because Widgets library itself would take advantage of it and could save various information in it. For example FontMapper or Unix version of FileDialog have the ability to use Config class.





Constructor and destructor



Path management

As explained in config overview, the config classes support a file system-like hierarchy of keys (files) and groups (directories). As in the file system case, to specify a key in the config class you must use a path to it. Config classes also support the notion of the current group, which makes it possible to use the relative paths. To clarify all this, here is an example (it is only for the sake of demonstration, it doesn’t do anything sensible!):

Config config = new Config("FooBarApp");
// right now the current path is '/'
conf->Write("RootEntry", 1);
// go to some other place: if the group(s) don't exist, they will be created
// create an entry in subgroup
conf->Write("SubgroupEntry", 3);
// '..' is understood
conf->Write("../GroupEntry", 2);
ASSERT( conf->Read("Subgroup/SubgroupEntry", 0l)  3 );
// use absolute path: it is allowed, too
ASSERT( conf->Read("/RootEntry", 0l)  1 );

Warning: it is probably a good idea to always restore the path to its old value on function exit:

void foo(ConfigBase *config)
  String strOldPath = config->GetPath();

because otherwise the assert in the following example will surely fail (we suppose here that foo() function is the same as above except that it doesn’t save and restore the path):

void bar(ConfigBase *config)
  config->Write("Test", 17);
// we're reading "/Foo/Data/Test" here! -1 will probably be returned...
ASSERT( config->Read("Test", -1) == 17 );

Finally, the path separator in ConfigBase and derived classes is always ’/’, regardless of the platform (i.e. it is *not ’$$’ under Windows).




The functions in this section allow to enumerate all entries and groups in the config file. All functions here return when there are no more items.

You must pass the same index to GetNext and GetFirst (don’t modify it). Please note that it is not the index of the current item (you will have some great surprises with RegConfig if you assume this) and you shouldn’t even look at it: it is just a “cookie” which stores the state of the enumeration. It can’t be stored inside the class because it would prevent you from running several enumerations simultaneously, that’s why you must pass it explicitly.

Having said all this, enumerating the config entries/groups is very simple:

ConfigBase config = ...;
ArrayString aNames;
// enumeration variables
String str;
long dummy;
// first enum all entries
bool bCont = config->GetFirstEntry(str, dummy);
while ( bCont ) {
bCont = GetConfig()->GetNextEntry(str, dummy);
... we have all entry names in aNames...
// now all groups...
bCont = GetConfig()->GetFirstGroup(str, dummy);
while ( bCont ) {
bCont = GetConfig()->GetNextGroup(str, dummy);
... we have all group (and entry) names in aNames...

There are also functions to get the number of entries/subgroups without actually enumerating them, but you will probably never need them.







Tests of existence





Miscellaneous functions




Key access

These function are the core of ConfigBase class: they allow you to read and write config file data. All Read function take a default value which will be returned if the specified key is not found in the config file.

Currently, only two types of data are supported: string and long (but it might change in the near future). To work with other types: for int or bool you can work with function taking/returning long and just use the casts. Better yet, just use long for all variables which you’re going to save in the config file: chances are that sizeof(bool) sizeof(int) sizeof(long) anyhow on your system. For float, double and, in general, any other type you’d have to translate them to/from string representation and use string functions.

Try not to read long values into string variables and vice versa: although it just might work with FileConfig, you will get a system error with RegConfig because in the Windows registry the different types of entries are indeed used.

Final remark: the szKey parameter for all these functions can contain an arbitrary path (either relative or absolute), not just the key name.




Rename entries/groups

The functions in this section allow to rename entries or subgroups of the current group. They will return on error. typically because either the entry/group with the original name doesn’t exist, because the entry/group with the new name already exists or because the function is not supported in this Config implementation.



Delete entries/groups

The functions in this section delete entries and/or groups of entries from the config file. DeleteAll() is especially useful if you want to erase all traces of your program presence: for example, when you uninstall it.





Some aspects of ConfigBase behaviour can be changed during run-time. The first of them is the expansion of environment variables in the string values read from the config file: for example, if you have the following in your config file: the call to config->Read("UserData") will return something like "/home/zeitlin/data" if you’re lucky enough to run a Linux system ;-)

  1. config file for my program UserData = $HOME/data
  1. the following syntax is valud only under Windows UserData =

Although this feature is very useful, it may be annoying if you read a value which containts ’\$’ or ’\’ symbols (\ is used for environment variables expansion under Windows) which are not used for environment variable expansion. In this situation you may call SetExpandEnvVars(false) just before reading this value and SetExpandEnvVars(true) just after. Another solution would be to prefix the offending symbols with a backslash.

The following functions control this option:








ConfigBase.newString% appName = '',  String vendorName = '', 
               String localFilename = '', 
               String globalFilename = '', 
               Integer style = 0, 
               MBConv conv = ConvUTF8)

This is the default and only constructor of the ConfigBase class, and derived classes.


The CONFIG_USE_NO_ESCAPE_CHARACTERS style can be helpful if your config file must be read or written to by a non-Widgets program (which might not understand the escape characters). Note, however, that if CONFIG_USE_NO_ESCAPE_CHARACTERS style is used, it is is now your application’s responsibility to ensure that there is no newline or other illegal characters in a value, before writing that value to the file.


By default, environment variable expansion is on and recording defaults is off.


Empty but ensures that dtor of all derived classes is virtual.


ConfigBase *create()

Create a new config object: this function will create the “best” implementation of Config available for the current platform, see comments near the definition of CONFIG_WIN32_NATIVE for details. It returns the created object and also sets it as the current one.



Calling this function will prevent Get() from automatically creating a new config object if the current one is NULL. It might be useful to call it near the program end to prevent “accidental” creation of a new config object.


Boolean delete_all()

Delete the whole underlying object (disk file, registry key, ...). Primarly for use by uninstallation routine.


Boolean delete_entry(String key,  Boolean bDeleteGroupIfEmpty = true)

Deletes the specified entry and the group it belongs to if it was the last key in it and the second parameter is true.


Boolean delete_group(String key)

Delete the group (with all subgroups)


Boolean exists(String strName)

returns if either a group or an entry with a given name exists


Boolean flush(Boolean bCurrentOnly = false)

permanently writes all changes (otherwise, they’re only written from object’s destructor)


ConfigBase get(Boolean CreateOnDemand = true)

Get the current config object. If there is no current object and CreateOnDemand is true, creates one (using Create) unless DontCreateOnDemand was called previously.


String get_app_name()

Returns the application name.


enum ConfigBase::EntryType get_entry_type(String name)

Returns the type of the given entry or Unknown if the entry doesn’t exist. This function should be used to decide which version of Read() should be used because some of Config implementations will complain about type mismatch otherwise: e.g., an attempt to read a string value from an integer key with RegConfig will fail.

The result is an element of enum EntryType:

enum EntryType


Boolean get_first_group(String str,  Integer index)

Gets the first group.


Boolean get_first_entry(String str,  Integer index)

Gets the first entry.


Boolean get_next_group(String str,  Integer index)

Gets the next group.


Boolean get_next_entry(String str,  Integer index)

Gets the next entry.


uint  get_number_of_entries(Boolean bRecursive = false)


uint get_number_of_groups(Boolean bRecursive = false)

Get number of entries/subgroups in the current group, with or without its subgroups.


String get_path()

Retrieve the current path (always as absolute path).


String get_vendor_name()

Returns the vendor name.


Boolean has_entry(String strName)

returns if the entry by this name exists


Boolean has_group(String strName)

returns if the group by this name exists


Boolean is_expanding_env_vars()

Returns if we are expanding environment variables in key values.


Boolean is_recording_defaults()

Returns if we are writing defaults back to the config file.


Boolean read(String key,  String str)

Read a string from the key, returning if the value was read. If the key was not found, str is not changed.

Boolean read(String key,  String str,  String defaultVal)

Read a string from the key. The default value is returned if the key was not found.

Returns if value was really read, if the default was used.

String read(String key,  String defaultVal)

Another version of Read(), returning the string value directly.

Boolean read(String key,  Integer l)

Reads a long value, returning if the value was found. If the value was not found, l is not changed.

Boolean read(String key,  Integer l, Integer defaultVal)

Reads a long value, returning if the value was found. If the value was not found, defaultVal is used instead.

long  read(String key,  Integer defaultVal)

Reads a long value from the key and returns it. defaultVal is returned if the key is not found.

NB: writing

conf->Read("key", 0);

won’t work because the call is ambiguous: compiler can not choose between two Read functions. Instead, write:

conf->Read("key", 0l);
Boolean read(String key,  Float d)

Reads a double value, returning if the value was found. If the value was not found, d is not changed.

Boolean read(String key,  Float d,  Float defaultVal)

Reads a double value, returning if the value was found. If the value was not found, defaultVal is used instead.

Boolean read(String key,  Boolean b)

Reads a bool value, returning if the value was found. If the value was not found, b is not changed.

Boolean read(String key,  Boolean d, Boolean defaultVal)

Reads a bool value, returning if the value was found. If the value was not found, defaultVal is used instead.


Boolean rename_entry(String oldName,  String newName)

Renames an entry in the current group. The entries names (both the old and the new one) shouldn’t contain backslashes, i.e. only simple names and not arbitrary paths are accepted by this function.

Returns if oldName doesn’t exist or if newName already exists.


Boolean rename_group(String oldName,  String newName)

Renames a subgroup of the current group. The subgroup names (both the old and the new one) shouldn’t contain backslashes, i.e. only simple names and not arbitrary paths are accepted by this function.

Returns if oldName doesn’t exist or if newName already exists.


ConfigBase set(ConfigBase pConfig)

Sets the config object as the current one, returns the pointer to the previous current object (both the parameter and returned value may be NULL)


set_expand_env_vars *(Boolean bDoIt = true)

Determine whether we wish to expand environment variables in key values.


set_pathString% strPath)

Set current path: if the first character is ’/’, it is the absolute path, otherwise it is a relative path. ’..’ is supported. If strPath doesn’t exist it is created.


set_record_defaultsBoolean% bDoIt = true)

Sets whether defaults are recorded to the config file whenever an attempt to read the value which is not present in it is done.

If on (default is off) all default values for the settings used by the program are written back to the config file. This allows the user to see what config options may be changed and is probably useful only for FileConfig.


Boolean *write(String key,  String value)
Boolean write(String key,  Integer value)
Boolean write(String key,  Float value)
Boolean write(String key,  Boolean value)

These functions write the specified value to the config file and return on success.

[This page automatically generated from the Textile source at Wed Sep 09 02:21:03 +0100 2009]