Classes

A class is a thematic group of a layer's features — for example "rock venues" versus "jazz venues". Each class has an optional expression that decides which features it matches, and contains the styles and labels used to render them. A class maps to a MapServer CLASS block.

Features are matched against classes in sortid order. When the layer property theme_column is set, a simple string expression like rock is compared against that column; without a theme_column, use logical expressions like ([capacity] > 1000). A class without an expression matches all features.

Get classes

Web App

HTTP

All classes of a layer

GET https://api.centia.io/api/v4/layers/rockhall.venues.the_geom/classes HTTP/1.1
Accept: application/json; charset=utf-8
Authorization: Bearer abc123

A specific class

GET https://api.centia.io/api/v4/layers/rockhall.venues.the_geom/classes/1 HTTP/1.1
Accept: application/json; charset=utf-8
Authorization: Bearer abc123

Add a class

The server assigns the class id — a request that includes an id is rejected with 400.

Web App

HTTP

Add a class with a nested style

POST https://api.centia.io/api/v4/layers/rockhall.venues.the_geom/classes HTTP/1.1
Content-Type: application/json
Authorization: Bearer abc123

{
    "name": "Large rock venues",
    "expression": "([capacity] > 1000)",
    "minscaledenom": "1000",
    "maxscaledenom": "250000",
    "styles": [
        {
            "symbol": "circle",
            "color": "#FF0000",
            "size": "14"
        }
    ]
}

Update a class

PATCH merges the keys you send into the class. Styles and labels are managed through their own routes — see Styles and Labels.

Change the expression

PATCH https://api.centia.io/api/v4/layers/rockhall.venues.the_geom/classes/1 HTTP/1.1
Content-Type: application/json
Authorization: Bearer abc123

{
    "expression": "([capacity] > 2000)"
}

Delete a class

DELETE https://api.centia.io/api/v4/layers/rockhall.venues.the_geom/classes/1 HTTP/1.1
Authorization: Bearer abc123

Class properties

Property	Description
id	Fixed, server-assigned id.
name	Class name, shown in the WMS legend.
expression	MapServer class expression. A plain string is matched against the layer's theme_column; logical expressions like ([capacity] > 1000) work without one.
sortid	Render/display order.
minscaledenom / maxscaledenom	Scale range in which the class is drawn.
leader	Boolean. Enables a MapServer LEADER block that connects a label to its feature with a line when the label is offset from its anchor.
leader_color	Color of the leader line. Defaults to black.
leader_gridstep	Grid step used to search for a valid label position. Defaults to 5.
leader_maxdistance	Maximum distance in pixels the label may be moved from the feature. Defaults to 30.
styles	The class's style entries.
labels	The class's label entries.