# IQueryEngineFilter > Interface for the QueryEngine filters. ## Definition * **Type:** Interface * **Namespace:** [UnityEditor.Search](/engine/6000.6/script-reference/unityeditor/search.md) * **Assembly:** UnityEditor ```csharp public interface IQueryEngineFilter ``` ## Remarks When you add a new filter on a [QueryEngine](/engine/6000.6/script-reference/unityeditor/search/queryengine1.md), you receive a filter object that implements the interface [IQueryEngineFilter](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter.md). You can modify this filter to override the global behaviors of the [QueryEngine](/engine/6000.6/script-reference/unityeditor/search/queryengine1.md). For example, you can add [type parsers](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/addtypeparser.md) or [operators](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/addoperator.md) that are specific to this filter. ## Examples ```csharp using System.Collections.Generic; using System.Globalization; using System.Linq; using UnityEditor; using UnityEditor.Search; using UnityEngine; static class Example_IQueryEngineFilter { static List s_Data; static QueryEngine SetupQueryEngine() { // Set up the query engine var queryEngine = new QueryEngine(); // Add a filter for MyObjectType.position that supports equals and not equals queryEngine.AddFilter("p", myObj => myObj.position, new[] { "=", "!=" }); #region add_filter_type_parser // Add a new type parser for Vector2 written as "[x, y]", but only for this filter. // This type parser will not affect other filters. queryEngine.TryGetFilter("p", out var filter); filter.AddTypeParser(s => { // If the format requirement is not met, return a failure. if (!s.StartsWith("[") || !s.EndsWith("]")) return ParseResult.none; var trimmed = s.Trim('[', ']'); var vectorTokens = trimmed.Split(','); var vectorValues = vectorTokens.Select(token => float.Parse(token, CultureInfo.InvariantCulture.NumberFormat)).ToList(); if (vectorValues.Count != 2) return ParseResult.none; var vector = new Vector2(vectorValues[0], vectorValues[1]); // When the conversion succeeds, return a success. return new ParseResult(true, vector); }); #endregion #region add_filter_operator_handlers // Override global operators with specific operator handlers for this filter filter.AddOperator("=").AddHandler((Vector2 ev, Vector2 fv) => ev == fv); filter.AddOperator("!=").AddHandler((Vector2 ev, Vector2 fv) => ev != fv); #endregion // Set up what data from objects of type MyObjectType will be matched against search words queryEngine.SetSearchDataCallback(myObj => new[] { myObj.id.ToString(), myObj.name }); return queryEngine; } [MenuItem("Examples/IQueryEngineFilter/IQueryEngineFilter")] public static void RunExample() { s_Data = GenerateExampleData(); var queryEngine = SetupQueryEngine(); TestFiltering(queryEngine, s_Data); } static void TestFiltering(QueryEngine queryEngine, IEnumerable inputData) { var vec = new Vector2(1, 0); // Find objects that are at position [1, 0] var filteredData = FilterData("p=[1,0]", queryEngine, inputData); ValidateData(filteredData, s_Data.Where(myObj => myObj.position == vec)); //Find objects that are not at position [1, 0] filteredData = FilterData("p!=[1,0]", queryEngine, inputData); ValidateData(filteredData, s_Data.Where(myObj => myObj.position != vec)); } static IEnumerable FilterData(string inputQuery, QueryEngine queryEngine, IEnumerable inputData) { // Parse the query string into a query operation var query = queryEngine.ParseQuery(inputQuery); // If the query is not valid, print all errors and return an empty data set if (!query.valid) { foreach (var queryError in query.errors) { Debug.LogFormat(LogType.Error, LogOption.NoStacktrace, null, $"Error parsing input at {queryError.index}: {queryError.reason}"); } return new List(); } // Apply the query on a data set and get the filtered result. var filteredData = query.Apply(inputData); return filteredData; } static void ValidateData(IEnumerable filteredData, IEnumerable expectedData) { var filteredDataArray = filteredData.ToArray(); var expectedDataArray = expectedData.ToArray(); Debug.Assert(filteredDataArray.Length == expectedDataArray.Length, $"Filtered data should have {expectedDataArray.Length} elements."); if (filteredDataArray.Length != expectedDataArray.Length) return; for (var i = 0; i < expectedDataArray.Length; i++) { Debug.Assert(filteredDataArray[i] == expectedDataArray[i], $"{filteredDataArray[i]} should be equal to {expectedDataArray[i]}"); } } static List GenerateExampleData() { var data = new List() { new MyObjectType { id = 0, name = "Test 1", position = new Vector2(0, 0), active = false }, new MyObjectType { id = 1, name = "Test 2", position = new Vector2(0, 1), active = true }, new MyObjectType { id = 2, name = "Test 3", position = new Vector2(1, 0), active = false }, new MyObjectType { id = 3, name = "Test 4", position = new Vector2(1.2f, 0), active = false }, }; return data; } /// /// Custom type. This is the type of objects that will be searched by the QueryEngine. /// class MyObjectType { public int id { get; set; } public string name { get; set; } public Vector2 position { get; set; } public bool active { get; set; } public MyObjectType() { id = 0; name = ""; position = Vector2.zero; active = false; } public override string ToString() { return $"({id}, {name}, ({position.x}, {position.y}), {active})"; } } } ``` ## Properties | Property | Description | | --------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- | | [metaInfo](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/metainfo.md) | Additional information specific to the filter. | | [operators](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/operators.md) | Collection of [QueryFilterOperators](/engine/6000.6/script-reference/unityeditor/search/queryfilteroperator.md) specific for the filter. | | [overridesStringComparison](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/overridesstringcomparison.md) | Indicates if the filter overrides the global string comparison options. | | [parameterType](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/parametertype.md) | The type of the constant parameter passed to the filter, if used. | | [regexToken](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/regextoken.md) | The regular expression that matches the filter. Matches what precedes the operator in a filter (for example. "id" in "id>=2"). | | [stringComparison](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/stringcomparison.md) | The string comparison options of the filter. | | [supportedOperators](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/supportedoperators.md) | List of supported operators. | | [token](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/token.md) | The identifier of the filter. Typically what precedes the operator in a filter (for example, "id" in "id>=2"). | | [type](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/type.md) | The type of the data that is compared by the filter. | | [usesParameter](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/usesparameter.md) | Indicates if the filter uses a parameter. | | [usesRegularExpressionToken](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/usesregularexpressiontoken.md) | Indicates if the filter uses a regular expression token or not. | | [usesResolver](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/usesresolver.md) | Indicates if the filter uses a resolver function. | ## Methods | Method | Description | | ------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [AddOperator](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/addoperator.md) | Add a custom filter operator specific to the filter. | | [AddOrUpdateMetaInfo](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/addorupdatemetainfo.md) | Add or update additional information specific to the filter. | | [AddTypeParser](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/addtypeparser.md) | Add a type parser specific to the filter. | | [ClearMetaInfo](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/clearmetainfo.md) | Removes all additional information specific to the filter. | | [RemoveMetaInfo](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/removemetainfo.md) | Remove information on the filter. | | [RemoveOperator](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/removeoperator.md) | Remove a custom operator specific to the filter. | | [SetNestedQueryTransformer](/engine/6000.6/script-reference/unityeditor/search/iqueryenginefilter/setnestedquerytransformer.md) | Sets the filter's nested query transformer function. This function takes the result of a nested query and extracts the necessary data to compare with the filter. |