Name
sflayer --- Manage Simple Features Layer
Syntax
sflayer getextent
sflayer topostscript
sflayer towkt fid
sflayer tokml fid
sflayer getfids
sflayer getfieldnames
sflayer getfield
sflayer fid fieldname
sflayer setfield fid fieldname value
sflayer setspatialfilterrect [minx miny maxx maxy]
sflayer setattributefilter [filter expression]
sflayer resetreading
sflayer getnextfid
Description
Programmatically manage a project object of type Simple Features Layer. The datasource must be the active project object, set using project activate or project setpath
Arguments
getextent
Return layer extent as a Tcl list { minx miny maxx maxy }
topostscript
Return the geometry of the layer as a sequence of Postscipt drawing commands. This will preserver inner polygons and polygon winding. Points are not supported.
towkt fid
Return the geometry of the given feature as well-known text. The fid argument is feature-id.
tokml fid
Return the geometry of the given feature as KML. The fid argument is feature-id.
getfids
Return the ids of all features in the layer as a Tcl list. If the spatial or attribute filters are set the feature set will be filtered accordingly.
getfieldnames
Return all column (field) names in the layer as a Tcl list.
getfield fid fieldname
Return value of given field in the feature identified by feature id fid.
setfield fid fieldname value
Set field value in column (field) given by fieldname in feature identified by given feature id fid.
sflayer setspatialfilterrect [minx miny maxx maxy]
Set spatial filter to given rectangle. Subsequent calls to getfids, resetreading, and getnextfid will only return features that geometrically intersect with the given rectangle. If the rectangle coordinates are omitted the spatial filter is reset.
sflayer setattributefilter [filter expression]
Filter features by expression. Subsequent calls to getfids, resetreading, and getnextfid will only return features that pass the filter expression. The expression is a WHERE expression similar to what is used in SQL. For example, if the layer contain columns 'state' and 'area' the expression
state = 'ohio' and area > 1000
would set the filter to return only features that pass the given criteria. Valid operators are =, <>, <, >, <=, >=, LIKE, and IN.
Use the LIKE operator to perform wildcard comparison. Use % (any character) and _ (one character) as wildcard placeholders. For example, the following expression will filter all features with values in the name column that has 'OR' as the second and third letter, while allowing any set of characters after that:
name LIKE '_OR%'
This could return PORTUGAL, NORWAY, MOROCCO, etc.
To reset the attribute filter omit the filter expression.
sflayer resetreading
Reset the feature cursor used for reading feature ids. The next call to getnextfid will return the id of the first feature id in the layer. Note that spatial filtering and attribute filtering still applies.
To read all feature ids in the layer:
sflayer resetreading
set fid [sflayer getnextfid]
while { $fid != "" } {
puts "Feature id is $fid"
set fid [sflayer getnextfid]
}
sflayer getnextfid
Return the next feature id and advance the feature cursor to the next feature ,as permitted by the spatial filtering and attribute filtering. See resetreading.