QGIS/resources/function_help/json/overlay_touches

{
  "name": "overlay_touches",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Returns whether the current feature spatially touches at least one feature from a target layer, or an array of expression-based results for the features in the target layer touched by the current feature.<br><br>Read more on the underlying GEOS \"Touches\" predicate, as described in PostGIS <a href='https://postgis.net/docs/ST_Touches.html'>ST_Touches</a> function.",
  "arguments": [{
    "arg": "layer",
    "description": "the layer whose overlay is checked"
  }, {
    "arg": "expression",
    "description": "an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.",
    "optional": true
  }, {
    "arg": "filter",
    "description": "an optional expression to filter the target features to check. If not set, all the features will be checked.",
    "optional": true
  }, {
    "arg": "limit",
    "description": "an optional integer to limit the number of matching features. If not set, all the matching features will be returned.",
    "optional": true
  }, {
    "arg": "cache",
    "description": "set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)",
    "optional": true,
    "default": "false"
  }],
  "examples": [{
    "expression": "overlay_touches('regions')",
    "returns": "TRUE if the current feature spatially touches a region"
  }, {
    "expression": "overlay_touches('regions', filter:= population > 10000)",
    "returns": "TRUE if the current feature spatially touches a region with a population greater than 10000"
  }, {
    "expression": "overlay_touches('regions', name)",
    "returns": "an array of names, for the regions touched by the current feature"
  }, {
    "expression": "string_to_array(overlay_touches('regions', name))",
    "returns": "a string as a comma separated list of names, for the regions touched by the current feature"
  }, {
    "expression": "array_sort(overlay_touches(layer:='regions', expression:=\"name\", filter:= population > 10000))",
    "returns": "an ordered array of names, for the regions touched by the current feature and with a population greater than 10000"
  }, {
    "expression": "overlay_touches(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2)",
    "returns": "an array of geometries (in WKT), for up to two regions touched by the current feature"
  }],
  "tags": ["predicate", "touches", "current", "target", "array", "geos", "touched", "st_touches", "features"]
}