JSON Support in Qt

Overview

JSON is a format to store structured data. It has 6 basic data types:

• bool
• double
• string
• array
• object
• null

Any value can be any of the above type. A boolean value is represented by the strings true or false in JSON. JSON doesn't explicitly specify the valid range for numbers, but the support in Qt is limited to the valid range and precision of doubles. A string can be any valid unicode string. An array is a list of values, and an object is a dictionary of key/value pairs. All keys in an object are strings, and an object cannot contain any duplicated keys.

The text representation, of JSON encloses arrays in square brackets ([ ... ]) and objects in curly brackets ({ ... }). The different entries in arrays and objects are separated by commas. The separator between keys and values in an object is a colon (:).

A simple JSON document encoding a person, its age, address and phone numbers could look like:

 {
     "FirstName": "John",
     "LastName": "Doe",
     "Age": 43,
     "Address": {
         "Street": "Downing Street 10",
         "City": "London",
         "Country": "Great Britain"
     },
     "Phone numbers": [
         "+44 1234567",
         "+44 2345678"
     ]
 }

The above example consists of an object with 5 key/value pairs. Two of the values are strings, one is a number, one is another object and the last one an array.

A valid JSON document is either an array or an object, so a document always starts with a square or curly bracket.

The JSON support in Qt consists of a set of 4 classes.