# QueryEngine > A QueryEngine defines how to build a query from an input string. It can be customized to support custom filters and operators. ## Definition * **Type:** Class * **Namespace:** [UnityEditor.Search](/engine/6000.7/script-reference/unityeditor/search.md) * **Assembly:** UnityEditor ```csharp public class QueryEngine ``` ## Remarks \\\: The filtered data type. ## Examples ```csharp using System.Collections.Generic; using System.Linq; using UnityEditor; using UnityEditor.Search; using UnityEngine; static class Example_QueryEngine { static List s_Data; static QueryEngine SetupQueryEngine() { // Set up the query engine var queryEngine = new QueryEngine(); #region basic_add_filter // Add a filter for MyObjectType.id that supports all operators queryEngine.AddFilter("id", myObj => myObj.id); // Add a filter for MyObjectType.name that supports only contains (:), equal (=) and not equal (!=) queryEngine.AddFilter("n", myObj => myObj.name, new[] { ":", "=", "!=" }); // Add a filter for MyObjectType.active that supports only equal and not equal queryEngine.AddFilter("a", myObj => myObj.active, new[] { "=", "!=" }); // Add a filter for the computed property magnitude that supports equal, not equal, lesser, greater, lesser or equal and greater or equal. queryEngine.AddFilter("m", myObj => myObj.position.magnitude, new[] { "=", "!=", "<", ">", "<=", ">=" }); #endregion #region basic_search_data_callback // Set up what data from objects of type MyObjectType will be matched against search words queryEngine.SetSearchDataCallback(myObj => new[] { myObj.id.ToString(), myObj.name }); #endregion return queryEngine; } [MenuItem("Examples/QueryEngine/Class")] public static void RunExample() { s_Data = GenerateExampleData(); var queryEngine = SetupQueryEngine(); TestFiltering(queryEngine, s_Data); } static void TestFiltering(QueryEngine queryEngine, IEnumerable inputData) { // Find objects that have an id > 2 and are active var filteredData = FilterData("id>2 a=true", queryEngine, inputData); ValidateData(filteredData, s_Data.Where(myObj => myObj.id > 2 && myObj.active)); // Find objects that are not active and have a name that contains Test filteredData = FilterData("a=false n:Test", queryEngine, inputData); ValidateData(filteredData, s_Data.Where(myObj => myObj.name.Contains("Test") && !myObj.active)); // Find objects that have a magnitude higher than 1 or the id 0. filteredData = FilterData("m>1 or id=0", queryEngine, inputData); ValidateData(filteredData, s_Data.Where(myObj => myObj.position.magnitude > 1f || myObj.id == 0)); } 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, 1), active = true }, new MyObjectType { id = 4, name = "Test 5", position = new Vector2(2, 0), active = false }, new MyObjectType { id = 5, name = "Test 6", position = new Vector2(0, 2), active = true } }; 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})"; } } } ``` ## Constructors | Constructor | Description | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------- | | [QueryEngine\`1()](/engine/6000.7/script-reference/unityeditor/search/queryengine1/ctor.md#queryengine\(\)) | Constructs a new QueryEngine. | | [QueryEngine\`1(System.Boolean)](/engine/6000.7/script-reference/unityeditor/search/queryengine1/ctor.md#queryengine\(bool\)) | Constructs a new QueryEngine. | | [QueryEngine\`1(UnityEditor.Search.QueryValidationOptions)](/engine/6000.7/script-reference/unityeditor/search/queryengine1/ctor.md#queryengine\(queryvalidationoptions\)) | Constructs a new QueryEngine. | ## Properties | Property | Description | | --------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [globalStringComparison](/engine/6000.7/script-reference/unityeditor/search/queryengine1/globalstringcomparison.md) | Global string comparison options for word matching and filter handling (if not overridden). | | [searchDataCallback](/engine/6000.7/script-reference/unityeditor/search/queryengine1/searchdatacallback.md) | The callback used to get the data to match to the search words. | | [searchDataOverridesStringComparison](/engine/6000.7/script-reference/unityeditor/search/queryengine1/searchdataoverridesstringcomparison.md) | Indicates if word/phrase matching uses searchDataStringComparison or not. | | [searchDataStringComparison](/engine/6000.7/script-reference/unityeditor/search/queryengine1/searchdatastringcomparison.md) | String comparison options for word/phrase matching. | | [searchWordMatcher](/engine/6000.7/script-reference/unityeditor/search/queryengine1/searchwordmatcher.md) | The function used to match the search data against the search words. | | [skipIncompleteFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/skipincompletefilters.md) | Boolean. Indicates if incomplete filters should be skipped. If true, filters are skipped. If false and [validateFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/validatefilters.md) is true, incomplete filters will generate errors when parsed. | | [skipUnknownFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/skipunknownfilters.md) | Boolean. Indicates if unknown filters should be skipped. If true, unknown filters are skipped. If false and [validateFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/validatefilters.md) is true, unknown filters will generate errors if no default filter handler is provided. | | [validateFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/validatefilters.md) | Get or set if the engine must validate filters when parsing the query. Defaults to true. | ## Methods | Method | Description | | --------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [AddFilter](/engine/6000.7/script-reference/unityeditor/search/queryengine1/addfilter.md) | Adds a new custom filter. | | [AddFiltersFromAttribute](/engine/6000.7/script-reference/unityeditor/search/queryengine1/addfiltersfromattribute.md) | Adds all custom filters that are identified with the method attribute TFilterAttribute. | | [AddNestedQueryAggregator](/engine/6000.7/script-reference/unityeditor/search/queryengine1/addnestedqueryaggregator.md) | Adds a new nested query aggregator. An aggregator is an operation that can be applied on a nested query to aggregate the results of the nested query according to certain criteria. | | [AddOperator](/engine/6000.7/script-reference/unityeditor/search/queryengine1/addoperator.md) | Adds a custom filter operator. | | [AddOperatorHandler](/engine/6000.7/script-reference/unityeditor/search/queryengine1/addoperatorhandler.md) | Adds a custom filter operator handler. | | [AddTypeParser](/engine/6000.7/script-reference/unityeditor/search/queryengine1/addtypeparser.md) | Adds a type parser that parses a string and returns a custom type. Used by custom operator handlers (see AddOperatorHandler). | | [ClearFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/clearfilters.md) | Removes all filters that were added on the [QueryEngine](/engine/6000.7/script-reference/unityeditor/search/queryengine1.md). | | [GetAllFilters](/engine/6000.7/script-reference/unityeditor/search/queryengine1/getallfilters.md) | Get all filters added on this [QueryEngine](/engine/6000.7/script-reference/unityeditor/search/queryengine1.md). | | [GetOperator](/engine/6000.7/script-reference/unityeditor/search/queryengine1/getoperator.md) | Get a custom operator added on the [QueryEngine](/engine/6000.7/script-reference/unityeditor/search/queryengine1.md). | | [ParseQuery](/engine/6000.7/script-reference/unityeditor/search/queryengine1/parsequery.md) | Parses a query string into a ParsedQuery operation. This ParsedQuery operation can then be used to filter any data set of type TData. | | [RemoveFilter](/engine/6000.7/script-reference/unityeditor/search/queryengine1/removefilter.md) | Removes a custom filter. | | [RemoveOperator](/engine/6000.7/script-reference/unityeditor/search/queryengine1/removeoperator.md) | Removes a custom operator that was added on the [QueryEngine](/engine/6000.7/script-reference/unityeditor/search/queryengine1.md). | | [SetDefaultFilter](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setdefaultfilter.md) | Sets the default filter handler for filters that were not registered. | | [SetDefaultParamFilter](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setdefaultparamfilter.md) | Sets the default filter handler for function filters that were not registered. | | [SetFilterNestedQueryTransformer](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setfilternestedquerytransformer.md) | Sets a 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. | | [SetGlobalStringComparisonOptions](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setglobalstringcomparisonoptions.md) | Sets global string comparison options. Used for word matching and filter handling (unless overridden by filter). | | [SetNestedQueryHandler](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setnestedqueryhandler.md) | Sets the function that will handle nested queries. Only one handler can be set. | | [SetSearchDataCallback](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setsearchdatacallback.md) | Sets the callback used to fetch the data that is matched against the search words. | | [SetSearchWordMatcher](/engine/6000.7/script-reference/unityeditor/search/queryengine1/setsearchwordmatcher.md) | Set the search word matching function to be used instead of the default one. Set to null to use the default. | | [TryGetFilter](/engine/6000.7/script-reference/unityeditor/search/queryengine1/trygetfilter.md) | Get a filter by its token. |