Component bdljsn_jsonliterals [Package bdljsn]

Provide user-defined literals for bdljsn::Json objects. More...

Namespaces
namespace	bdljsn

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Detailed Description

Outline

• Purpose
• Classes
• Description
  • Use of the Global Allocator
  • Usage
    • Example 1: Creating a bdljsn::Json Object with a User Defined Literal

Purpose:

Provide user-defined literals for bdljsn::Json objects.

Classes:

bdljsn::JsonLiterals

a namespace for user-defined literal operators

Description:

This component provides a namespace, bdljsn::JsonLiterals, in which operators for the user-defined literal suffix "_json" are defined. Users can define a using declaration for the JsonLiterals namespace, and apply the "_json" suffix to literal text containing JSON to create bdljsn::Json objects (on platforms that support user defined literals).

For example:

  using namespace bdljsn::JsonLiterals;
  bdljsn::Json json = R"({"price": 2.1})"_json;

Use of the Global Allocator:

The operator "" _json returns a bdljsn::Json object that allocates memory using the currently installed global allocator. Using the global allocator prevents inadvertently locking the default allocator, as may happen before main when using a JSON literal to initialize an object at global file-scope static storage duration. Note that while file scoped static objects can be useful in testing, we discourage their use in production code.

Usage:

This section illustrates the intended use of this component.

Example 1: Creating a bdljsn::Json Object with a User Defined Literal:

This component provides a namespace in which user-defined literal operators for bdljsn::Json are defined. In this example we use a _json literal to initialize a bdljsn::Json object.

First, we define a user declaration for the appropriate namespace:

  using namespace bdljsn::JsonLiterals;

Then we create a bdljsn::Json object:

  bdljsn::Json json = R"({ "number": 4, "array": [0, 2, null] })"_json;

  assert(bdljsn::JsonType::e_NUMBER == json["number"].type());
  assert(bdljsn::JsonType::e_ARRAY  == json["array"].type());

Notice that the user-defined literal operator will unconditionally invoke the bsls::Assert handler if the literal text is not valid JSON.