Class: Getting and setting entity values.
[Query Object Framework]

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Detailed Description

This file defines a class messaging system reminiscent of traditional OO-style setter and getter interfaces to object properties. A C-language object can declare a collection of setters and getters on itself that can then be used to perform run-time (as opposed to compile-time) bindings to the object.

To put it differently, a QOF class is a set of parameter getters and setters that are associated with an object type. Given a pointer to some thing, the setters and getters can be used to get and set values out of that thing. Note that the pointer to "some thing" need not be a pointer to a QOF Entity or Instance (although QOF classes are more interesting when used with Entities/Instances). What "some thing" is defined entirely by the programmer declaring a new QOF Class.

Because a QOF Class associates getters and setters with a type, one can then ask, at run time, what parameters are associated with a given type, even if those parameters were not known at compile time. Thus, a QOF Class is sort-of like a DynAny implementation. QOF classes can be used to provide "object introspection", i.e. asking object to describe itself.

The QOF Query subsystem depends on QOF classes having been declared; the Query uses the getters to get values associated with particular instances.

A QofAccessFunc or QofSetterFunc do not need to be public functions, if you need to add functions to an object with an established API, define the additional QOF routines as static. Only the register routine needs to be public.

Files
file	qofclass.h
	API for registering paramters on objects.
Modules
	GUID
	Entity
	Instance
Data Structures
struct	_QofParam
Core types
Core data types for objects that can be used in parameters. Note that QofIdTypes may also be used and will create a single reference between two known objects.
#define	QOF_TYPE_STRING   "string"
#define	QOF_TYPE_TIME   "time"
#define	QOF_TYPE_NUMERIC   "numeric"
#define	QOF_TYPE_DEBCRED   "debcred"
#define	QOF_TYPE_GUID   "guid"
#define	QOF_TYPE_INT32   "gint32"
#define	QOF_TYPE_INT64   "gint64"
#define	QOF_TYPE_DOUBLE   "double"
#define	QOF_TYPE_BOOLEAN   "boolean"
#define	QOF_TYPE_KVP   "kvp"
#define	QOF_TYPE_CHAR   "character"
#define	QOF_TYPE_COLLECT   "collection"
Defines
#define	QOF_MOD_CLASS   "qof-class"
Typedefs
typedef const gchar *	QofType
typedef struct _QofParam	QofParam
typedef gpointer(*	QofAccessFunc )(gpointer object, const QofParam *param)
typedef void(*	QofSetterFunc )(gpointer, gpointer)
typedef gint(*	QofSortFunc )(gconstpointer, gconstpointer)
typedef void(*	QofClassForeachCB )(QofIdTypeConst, gpointer)
typedef void(*	QofParamForeachCB )(QofParam *, gpointer user_data)
Functions
void	qof_class_register (QofIdTypeConst obj_name, QofSortFunc default_sort_fcn, const QofParam *params)
	registers a new object class with the Qof subsystem.
gboolean	qof_class_is_registered (QofIdTypeConst obj_name)
QofType	qof_class_get_parameter_type (QofIdTypeConst obj_name, const gchar *param_name)
const QofParam *	qof_class_get_parameter (QofIdTypeConst obj_name, const gchar *parameter)
QofAccessFunc	qof_class_get_parameter_getter (QofIdTypeConst obj_name, const gchar *parameter)
QofSetterFunc	qof_class_get_parameter_setter (QofIdTypeConst obj_name, const gchar *parameter)
void	qof_class_foreach (QofClassForeachCB, gpointer user_data)
void	qof_class_param_foreach (QofIdTypeConst obj_name, QofParamForeachCB, gpointer user_data)
GList *	qof_class_get_referenceList (QofIdTypeConst type)
	List of the parameters that could be references.

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Define Documentation

#define QOF_TYPE_COLLECT   "collection"

secondary collections are used for one-to-many references between entities and are implemented using QofCollection. These are NOT the same as the main collections in the QofBook.

1. Each QofCollection contains one or many entities - *all* of a single type.
2. The entity type within the collection can be determined at run time.
3. Easy conversions to GList or whatever in the param_setfcn handler.
4. Each parameter can have its own collection.
5. Each entity can have a different *type* of collection to its siblings, provided that it is acceptable to the set function.
6. Each object decides which types are acceptable for which parameter in the set functions. This is then part of the API for that object.

QOF_TYPE_COLLECT has two functions, both related to one-to-many links:

• Represent a reference between 2 entities with a list of acceptable types. (one object linked to many types of single entities)
• Represent a reference between one entity and many entities of another type. (one object linked to many entities of a single type.)

If the set function can handle it, it could also be used for true one-to-many links: one object linked to many entities of many types.

n.b. Always subject to each collection holding only one type at runtime. (otherwise use books).

Definition at line 93 of file qofclass.h.

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Typedef Documentation

typedef gpointer(* QofAccessFunc)(gpointer object, const QofParam *param)

The QofAccessFunc defines an arbitrary function pointer for access functions. This is needed because C doesn't have templates, so we just cast a lot. Real functions must be of the form:

param_type getter_func (object_type *self); or param_type getter_func (object_type *self, QofParam *param);

The additional argument 'param' allows generic getter functions to be implemented, because this argument provides for a way to identify the expected getter_func return type at runtime. It also provides a place for the user to hang additional user-defined data.

Definition at line 142 of file qofclass.h.

typedef void(* QofClassForeachCB)(QofIdTypeConst, gpointer)

Type definition for the class callback function.

Definition at line 248 of file qofclass.h.

typedef void(* QofParamForeachCB)(QofParam *, gpointer user_data)

Type definition for the paramter callback function.

Definition at line 257 of file qofclass.h.

typedef void(* QofSetterFunc)(gpointer, gpointer)

The QofSetterFunc defines an function pointer for parameter setters. Real functions must be of the form:

void setter_func (object_type *self, param_type *param);

Definition at line 149 of file qofclass.h.

typedef gint(* QofSortFunc)(gconstpointer, gconstpointer)

This function is the default sort function for a particular object type

Definition at line 179 of file qofclass.h.

typedef const gchar* QofType

Type of Paramters (String, Date, Numeric, GUID, etc.)

Definition at line 123 of file qofclass.h.

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Function Documentation

void qof_class_foreach	(	QofClassForeachCB	,
		gpointer	user_data
	)

Call the callback once for each object class that is registered with the system. The 'user_data' is passed back to the callback.

Definition at line 233 of file qofclass.c.

{
    struct class_iterate qiter;

    if (!cb)
        return;
    if (!classTable)
        return;

    qiter.fcn = cb;
    qiter.data = user_data;

    g_hash_table_foreach (classTable, class_foreach_cb, &qiter);
}

const QofParam* qof_class_get_parameter	(	QofIdTypeConst	obj_name,
		const gchar *	parameter
	)

Return the registered Parameter Definition for the requested parameter

Definition at line 146 of file qofclass.c.

{
    GHashTable *ht;

    g_return_val_if_fail (obj_name, NULL);
    g_return_val_if_fail (parameter, NULL);
    if (!check_init ())
        return NULL;

    ht = g_hash_table_lookup (classTable, obj_name);
    if (!ht)
    {
        PWARN ("no object of type %s", obj_name);
        return NULL;
    }

    return (g_hash_table_lookup (ht, parameter));
}

QofAccessFunc qof_class_get_parameter_getter	(	QofIdTypeConst	obj_name,
		const gchar *	parameter
	)

Return the object's parameter getter function

Definition at line 166 of file qofclass.c.

{
    const QofParam *prm;

    g_return_val_if_fail (obj_name, NULL);
    g_return_val_if_fail (parameter, NULL);

    prm = qof_class_get_parameter (obj_name, parameter);
    if (prm)
        return prm->param_getfcn;

    return NULL;
}

QofSetterFunc qof_class_get_parameter_setter	(	QofIdTypeConst	obj_name,
		const gchar *	parameter
	)

Return the object's parameter setter function

Definition at line 182 of file qofclass.c.

{
    const QofParam *prm;

    g_return_val_if_fail (obj_name, NULL);
    g_return_val_if_fail (parameter, NULL);

    prm = qof_class_get_parameter (obj_name, parameter);
    if (prm)
        return prm->param_setfcn;

    return NULL;
}

QofType qof_class_get_parameter_type	(	QofIdTypeConst	obj_name,
		const gchar *	param_name
	)

Return the core datatype of the specified object's parameter

Definition at line 198 of file qofclass.c.

{
    const QofParam *prm;

    if (!obj_name || !param_name)
        return NULL;

    prm = qof_class_get_parameter (obj_name, param_name);
    if (!prm)
        return NULL;

    return (prm->param_type);
}

GList* qof_class_get_referenceList

(

QofIdTypeConst

type

)

List of the parameters that could be references.

Simple check to return a GList of all parameters of this object type that are not known QOF data types. Used for partial QofBook support, see QofEntityReference

Definition at line 332 of file qofclass.c.

{
    GList *ref_list;
    struct param_ref_list b;

    ref_list = NULL;
    b.list = NULL;
    qof_class_param_foreach (type, find_reference_param_cb, &b);
    ref_list = g_list_copy (b.list);
    return ref_list;
}

gboolean qof_class_is_registered

(

QofIdTypeConst

obj_name

)

An example:

define MY_OBJ_MEMO "memo" define MY_OBJ_VALUE "value" define MY_OBJ_TIME "time" define MY_OBJ_ACCOUNT "account" define MY_OBJ_TRANS "trans"

static QofParam myParams[] = { { MY_OBJ_MEMO, QOF_TYPE_STRING, myMemoGetter, NULL }, { MY_OBJ_VALUE, QOF_TYPE_NUMERIC, myValueGetter, NULL }, { MY_OBJ_TIME, QOF_TYPE_TIME, myTimeGetter, NULL }, { MY_OBJ_ACCOUNT, GNC_ID_ACCOUNT, myAccountGetter, NULL }, { MY_OBJ_TRANS, GNC_ID_TRANS, myTransactionGetter, NULL }, NULL };

qof_class_register ("myObjectName", myObjectCompare, &myParams); Return true if the the indicated type is registered, else return FALSE.

Definition at line 132 of file qofclass.c.

{
    if (!obj_name)
        return FALSE;
    if (!check_init ())
        return FALSE;

    if (g_hash_table_lookup (classTable, obj_name))
        return TRUE;

    return FALSE;
}

void qof_class_param_foreach	(	QofIdTypeConst	obj_name,
		QofParamForeachCB	,
		gpointer	user_data
	)

Call the callback once for each parameter on the indicated object class. The 'user_data' is passed back to the callback.

Definition at line 267 of file qofclass.c.

{
    struct parm_iterate qiter;
    GHashTable *param_ht;

    if (!obj_name || !cb)
        return;
    if (!classTable)
        return;
    param_ht = g_hash_table_lookup (classTable, obj_name);
    if (!param_ht)
        return;

    qiter.fcn = cb;
    qiter.data = user_data;

    g_hash_table_foreach (param_ht, param_foreach_cb, &qiter);
}

void qof_class_register	(	QofIdTypeConst	obj_name,
		QofSortFunc	default_sort_fcn,
		const QofParam *	params
	)

registers a new object class with the Qof subsystem.

In particular, it registers the set of setters and getters for controlling the object. The getters are typically used by the query subsystem to query type specific data. Note that there is no particular requirement for there to be a setter for every getter or even vice-versa, nor is there any requirement for these to map 'cleanly' or orthogonally to the underlying object. The parameters are really just a set of value setting and getting routines.

The "params" argument must be a NULL-terminated array of QofParam with a constant storage size. It may be NULL if there are no parameters to be registered. When creating dynamic QofObjects, ensure the array is long enough for all objects. Registration will stop at the first NULL parameter.

Definition at line 93 of file qofclass.c.

{
    GHashTable *ht;
    int i;

    if (!obj_name)
        return;
    if (!check_init ())
        return;

    if (default_sort_function)
    {
        g_hash_table_insert (sortTable, (gchar *) obj_name,
            default_sort_function);
    }

    ht = g_hash_table_lookup (classTable, obj_name);

    /* If it doesn't already exist, create a new table for this object */
    if (!ht)
    {
        ht = g_hash_table_new (g_str_hash, g_str_equal);
        g_hash_table_insert (classTable, (gchar *) obj_name, ht);
    }

    /* At least right now, we allow dummy, parameterless objects,
     * for testing purposes.  Although I suppose that should be
     * an error..  */
    /* Now insert all the parameters */
    if (params)
    {
        for (i = 0; params[i].param_name; i++)
            g_hash_table_insert (ht,
                (char *) params[i].param_name, (gpointer) & (params[i]));
    }
}

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