QGIS/resources/function_help/json/display_expression

{
  "name": "display_expression",
  "type": "function",
  "groups": ["Record and Attributes"],
  "description": "Returns the display expression for a given feature in a layer. The expression is evaluated by default. Can be used with zero, one or more arguments, see below for details.",
  "variants": [
    {
      "variant": "No parameters",
      "variant_description": "If called with no parameters, the function will evaluate the display expression of the current feature in the current layer.",
      "arguments": [],
      "examples": [ { "expression": "display_expression()", "returns" : "The display expression of the current feature in the current layer." } ]
    },
    {
      "variant": "One 'feature' parameter",
      "variant_description": "If called with a 'feature' parameter only, the function will evaluate the specified feature from the current layer.",
      "arguments": [ { "arg": "feature", "description": "The feature which should be evaluated." } ],
      "examples": [ { "expression": "display_expression(@atlas_feature)", "returns": "The display expression of the current atlas feature." } ]
    },
    {
      "variant" : "Layer and feature parameters",
      "variant_description": "If the function is called with both a layer and a feature, it will evaluate the specified feature from the specified layer.",
      "arguments": [
        { "arg": "layer", "description": "The layer (or its ID or name)" },
        { "arg": "feature", "description": "The feature which should be evaluated." },
        { "arg": "evaluate", "description": "If the expression must be evaluated. If false, the expression will be returned as a string literal only (which could potentially be later evaluated using the 'eval' function).", "optional": true, "default": "true" }
      ],
      "examples": [
        { "expression": "display_expression( 'streets', get_feature_by_id('streets', 1))",
          "returns": "The display expression of the feature with the ID 1 on the layer 'streets'."
        },
        { "expression": "display_expression('a_layer_id', $currentfeature, 'False')",
          "returns": "The display expression of the given feature not evaluated."
        }
      ]
    }
  ]
}