Changes between Initial Version and Version 1 of Future/ConvenienceApis

Timestamp:

Jul 23, 2013, 10:41:42 PM (11 years ago)

Author:

jng

Comment:

--

Future/ConvenienceApis

@@ +1 @@
+[[PageOutline]]
+
+This page is part of the [wiki:Future MapGuide Future] section, where ideas are proposed and refined 
+before being turned into RFCs (or discarded).  Visit the [wiki:Future] page to view more!
+
+= Overview =
+
+This page is a living proposal for adding extra convenience methods to the MapGuide API
+
+= Motivation =
+
+There are common scenarios in MapGuide application development where there is still lots of boilerplate code required to achieve desired tasks. Some of these scenarios are described below
+
+== Simplifying feature manipulation ==
+
+=== Inserting features ===
+
+The current process of inserting features is currently:
+
+ 1. Create a MgFeatureCommandCollection
+ 2. Create a MgPropertyCollection
+ 3. Populate the property collection with desired property values 
+ 4. Create a MgInsertFeatures
+ 5. Add the property collection to the MgInsertFeatures command
+ 6. Add the MgInsertFeatures command to the MgFeatureCommandCollection
+ 7. Execute MgFeatureService::UpdateFeatures passing in the feature source id and the command collection and to specify whether this should be transactional or not
+ 8. Process each individual result of the UpdateFeatures() call, taking note of any thrown exceptions (non-transactional) and open feature readers
+
+There is a lot of object creation and setup to insert a feature. Inserting multiple features increases the number of objects created and boilerplate code.
+
+mg-desktop provides a simplified API for inserting features, that should also be brought over to the MapGuide API:
+
+{{{
+
+class MG_PLATFORMBASE_API MgFeatureService : public MgService
+{
+PUBLISHED_API:
+    MgFeatureReader* InsertFeatures(MgResourceIdentifier* resource, CREFSTRING className, MgPropertyCollection* props);
+    MgFeatureReader* InsertFeatures(MgResourceIdentifier* resource, CREFSTRING className, MgPropertyCollection* props, MgTransaction* trans);
+    MgPropertyCollection* InsertFeatures(MgResourceIdentifier* resource, CREFSTRING className, MgBatchPropertyCollection* batchPropertyValues);
+    MgPropertyCollection* InsertFeatures(MgResourceIdentifier* resource, CREFSTRING className, MgBatchPropertyCollection* batchPropertyValues, MgTransaction* trans);
+};
+
+class MG_PLATFORMBASE_API MgLayerBase : public MgNamedSerializable
+{
+PUBLISHED_API:
+    MgFeatureReader* InsertFeatures(MgPropertyCollection* props);
+    MgFeatureReader* InsertFeatures(MgPropertyCollection* props, MgTransaction* trans);
+    MgPropertyCollection* InsertFeatures(MgBatchPropertyCollection* batchPropertyValues);
+    MgPropertyCollection* InsertFeatures(MgBatchPropertyCollection* batchPropertyValues, MgTransaction* trans);
+};
+
+}}}
+
+Under this simplified API, the process is now.
+
+ 1. Create a MgPropertyCollection or MgBatchPropertyCollection
+ 2. Load it up with the desired property values
+ 3. Execute InsertFeatures(), passing in the feature source, the property collection and optionally a transaction.
+ 4. Close the open feature reader, or process the property collection (if using a MgBatchPropertyCollection)
+
+=== Updating features ===
+
+The current process of update features is similarly complex:
+
+ 1. Create a MgFeatureCommandCollection
+ 2. Create a MgPropertyCollection
+ 3. Populate the property collection with desired property values to update
+ 4. Create a MgUpdateFeatures
+ 5. Add the property collection to the MgUpdateFeatures command
+ 6. Specify the update filter for the MgUpdateFeatures command
+ 7. Add the MgUpdateFeaturescommand to the MgFeatureCommandCollection
+ 8. Execute MgFeatureService::UpdateFeatures passing in the feature source id and the command collection and to specify whether this should be transactional or not
+ 9. Process each individual result of the UpdateFeatures() call, taking note of any thrown exceptions (non-transactional) and open feature readers
+
+There is a lot of object creation and setup to insert a feature. Inserting multiple features increases the number of objects created and boilerplate code.
+
+mg-desktop provides a simplified API for updating features, that should also be brought over to the MapGuide API:
+
+{{{
+
+class MG_PLATFORMBASE_API MgFeatureService : public MgService
+{
+PUBLISHED_API:
+    INT32 UpdateFeatures(MgResourceIdentifier* resource, CREFSTRING className, MgPropertyCollection* props, CREFSTRING filter);
+    INT32 UpdateFeatures(MgResourceIdentifier* resource, CREFSTRING className, MgPropertyCollection* props, CREFSTRING filter, MgTransaction* trans);
+};
+
+class MG_PLATFORMBASE_API MgLayerBase : public MgNamedSerializable
+{
+PUBLISHED_API:
+    INT32 UpdateFeatures(MgPropertyCollection* props, CREFSTRING filter);
+    INT32 UpdateFeatures(MgPropertyCollection* props, CREFSTRING filter, MgTransaction* trans);
+};
+
+}}}
+
+Under this simplified API, the process is now.
+
+ 1. Create a MgPropertyCollection
+ 2. Load it up with the desired property values to update with
+ 3. Execute UpdateFeatures(), passing in the feature source, the property collection, update filter and optionally a transaction.
+
+=== Deleting Features ===
+
+== Querying transformed features ==
+
+This API is currently not implemented in MapGuide
+
+{{{
+class MG_PLATFORMBASE_API MgFeatureService : public MgService
+{
+PUBLISHED_API:
+    virtual MgFeatureReader* SelectFeatures(MgResourceIdentifier* resource,
+                                            CREFSTRING className,
+                                            MgFeatureQueryOptions* options,
+                                            CREFSTRING coordinateSystem) = 0;
+};
+}}}
+
+Having this API implemented would be very useful. Along the same theme of convenience, MgLayerBase should have a shortcut form of the above API:
+
+{{{
+class MG_PLATFORMBASE_API MgLayerBase : public MgNamedSerializable
+{
+PUBLISHED_API:
+    virtual MgFeatureReader* SelectFeatures(MgFeatureQueryOptions* options,
+                                            CREFSTRING coordinateSystem);
+};
+}}}
+
+== Getting a layer icon ==
+
+The process to get the legend image icon for a given MgLayer instance is especially cumbersome as a lot of boilerplate code is required in fetching the associated layer definition and walking through its styles to get the matching geometry type and theme category required for a MgMappingService::GenerateLegendImage() call.
+
+Since MgLayer possesses most of this knowledge, it makes sense to have convenience APIs in MgLayer itself:
+
+{{{
+
+class MG_MAPGUIDE_API MgLayer : public MgLayerBase
+{
+PUBLISHED_API:
+    //Gets the list of geometry type styles for this layer at the map's current scale
+    MgIntCollection* GetGeometryTypeStyles();
+    //Gets the number of theme categories for this layer at the map's current scale for the given geometry type style. A count greater than 1 indicates a themed layer
+    INT32 GetThemeCategoryCount(INT32 geomType);
+    //Gets the legend image icon for this layer at the at the map's current scale for the given geometry type style and theme category
+    MgByteReader* GenerateLegendImage(INT32 width, INT32 height, CREFSTRING format, INT32 geomType, INT32 themeCategory);
+
+    //Gets the list of geometry type styles for this layer at the given scale
+    MgIntCollection* GetGeometryTypeStyles(double scale);
+    //Gets the number of theme categories for this layer at the given scale for the given geometry type style. A count greater than 1 indicates a themed layer
+    INT32 GetThemeCategoryCount(double scale, INT32 geomType);
+    //Gets the legend image icon for this layer at the at the given scale for the given geometry type style and theme category
+    MgByteReader* GenerateLegendImage(double scale, INT32 width, INT32 height, CREFSTRING format, INT32 geomType, INT32 themeCategory);
+};
+
+}}}