Keyword ‘index’

• Special keyword index can be used in lambda functions used with collections and its value is a 0 based index of a collection item being iterated.

• The index keyword can be used in some scenarios such as selecting only range of items from a collection.

Example

Note

The following JSON files are referenced in JsonQL expressions in Example.json in example below: Companies.json.

Example.json below demonstrates using index function.

{
  "TestArray": [ 1, 3, 7, 9, 11, 13 ],

  "SelectTheFirstThreeEmployees": "$value(Companies.Select(c => c.Employees).Where(e => index <= 2))",
  "SelectAllItemsExceptFirstAndLast": "$value(TestArray.Where(x => index > 0 && index < Count(TestArray) - 1))"
}

The result (i.e., an instance of JsonQL.Compilation.ICompilationResult) is serialized to a Result.json file below.

Note

For brevity, the serialized result includes only serialized evaluated Example.json and does not include parent JSON files in JsonQL.Compilation.ICompilationResult.CompiledJsonFiles

{
  "CompiledJsonFiles":[
    {
      "TextIdentifier": "Example",
      "CompiledParsedValue":
      {
        "TestArray": [
          1,
          3,
          7,
          9,
          11,
          13
        ],
        "SelectTheFirstThreeEmployees": [
          {
            "Id":  100000001,
            "Name":  "John Smith",
            "Address": {
              "Street":  "456 Oak Avenue",
              "City":  "Chicago",
              "State":  "IL",
              "ZipCode":  "60601"
            },
            "Salary":  99500,
            "Age":  45
          },
          {
            "Id":  100000002,
            "Name":  "Alice Johnson",
            "Address": {
              "Street":  "123 Maple Street",
              "City":  "New York",
              "State":  "NY",
              "ZipCode":  "10001"
            },
            "Salary":  105000,
            "Age":  38
          },
          {
            "Id":  100000003,
            "Name":  "Michael Brown",
            "Address": {
              "Street":  "789 Pine Lane",
              "City":  "Los Angeles",
              "State":  "CA",
              "ZipCode":  "90001"
            },
            "Salary":  89000,
            "Age":  50
          }
        ],
        "SelectAllItemsExceptFirstAndLast": [
          3,
          7,
          9,
          11
        ]
      }
    }
  ],
  "CompilationErrors":
  {
    "$type": "System.Collections.Generic.List`1[[JsonQL.Compilation.ICompilationErrorItem, JsonQL]], System.Private.CoreLib",
    "$values": []
  }
}

The code snippet shows how the JSON file Example.json was parsed using JsonQL.Compilation.IJsonCompiler

// Set the value of jsonCompiler to an instance of JsonQL.Compilation.IJsonCompiler here.
// The value of JsonQL.Compilation.JsonCompiler is normally created by Dependency Injection container
// and it is normally configured as a singleton.
JsonQL.Compilation.IJsonCompiler jsonCompiler = null!;

var sharedExamplesFolderPath = new []
{
    "DocFiles", "MutatingJsonFiles", "Examples"
};

var companiesJsonTextData = new JsonTextData("Companies",
    LoadJsonFileHelpers.LoadJsonFile("Companies.json", sharedExamplesFolderPath));

var result = jsonCompiler.Compile(new JsonTextData("Example",
    this.LoadExampleJsonFile("Example.json"), companiesJsonTextData));