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JSON library for Delphi

This is a small and clean library for associative arrays with Boolean / Integer / Float / WideString values. Allows import (export) from (to) JSON text. Extensive error-checking.

Some open-source projects I would like to give credit:

The library was built for the ease of use and clean understandable code - performance was not a first priority so I have not made any benchmarking.

Features

  • Numeric and WideString indexes (similar to PHP arrays)
  • Boolean / Int64 / Double / WideString item values
  • Strict parsing of JSON with descriptive Exception on error
  • Simple interface (Add, Delete, Remove, Clear)
  • Simple iterators (First, Last, Prev, Next)

Types of node values

Name Description
jsNull The NULL value
jsBool Node value is Boolean
jsInt Node value is Integer
jsFloat Node value is Floating-point
jsString Node value is String
jsArray Node is an array - has children

Iterators

  • TJSONEnum = procedure (Nomer: Integer; Elem: TJSONbase; Data: Pointer; Var Stop: Boolean);
  • TJSONEnumObj = procedure (Nomer: Integer; Elem: TJSONbase; Data: Pointer; Var Stop: Boolean) Of Object;

Parsing

function ParseJSON(JSON_str: PAnsiChar): TJSONbase;

Properties

Name Type Description
Assoc Boolean Whether all keys are Numeric or at least one key is String
Parent TJSONbase Where the given node belongs to
FirstChild TJSONbase Childs are organized as a double-linked list
LastChild TJSONbase Childs are organized as a double-linked list
Next TJSONbase Next sibling (by the order of creation)
Prev TJSONbase Previous sibling (by the order of creation)
SelfType TJSONtype Type of data in the current node
Value Variant Value of the current node
Count Integer Number of children if the node is non-scalar
Name WideString The String key of the current node if this is an associative array
ID Integer The Numeric key of the current node if this is non-associative array
Child[Index: Integer] TJSONbase Used to access the children of non-associative arrays
Field[Key: WideString] TJSONbase Used to access the children of associatve arrays
JsonText AnsiString Stringification of the current node as JSON text

Methods

Name Parameters Returns Description
Clear Remove all children
Delete Idx: Integer Delete a child from non-associative array and free the object
Delete Key: WideString Delete a child from associative array and free the object
Remove Idx: Integer TJSONbase Removee a child from non-associative array and return the object
Remove Key: WideString TJSONbase Remove a child from associative array and return the object
ForEach Iterator: TJSONEnum
UserData: Pointer		 Iterates over the children of non-associative array
ForEach Iterator: TJSONEnumObj
UserData: Pointer		 Iterates over the children of associative array
Add B: Boolean TJSONbase Appends a new Boolean child to the node (making it an array if not already, returns the new child)
Add I: Int64 TJSONbase Appends a new Integer child to the node (making it an array if not already, returns the new child)
Add D: Double TJSONbase Appends a new Floating-point child to the node (making it an array if not already, returns the new child)
Add S: WideString TJSONbase Appends a new String child to the node (making it an array if not already, returns the new child)
Add A: TJSONbase Appends an existing array as a child to the node (making it an array if not already
Add Key: WideString
B: Boolean		 TJSONbase Appends a new Boolean child to the node (making it an array if not already, returns the new child)
Add Key: WideString
I: Int64		 TJSONbase Appends a new Integer child to the node (making it an array if not already, returns the new child)
Add Key: WideString
D: Double		 TJSONbase Appends a new Floating-point child to the node (making it an array if not already, returns the new child)
Add Key: WideString
S: WideString		 TJSONbase Appends a new String child to the node (making it an array if not already, returns the new child)
Add Key: WideString
A: TJSONbase		 Appends an existing array as a child to the node (making it an array if not already

Possible errors

  • Unsupported assignment of object
  • Automatic indexing overflow
  • Invalid data type assigned to TJSONbase
  • This is an array - it does not have a value by itself
  • Index is outside the array
  • TJSONbase is not an array and does not support indexes
  • Associative arrays do not support empty index
  • TJSONbase is not an array and does not have Count property
  • Unsupported data type in TJSONbase.JsonText
  • Unexpected character at position
  • Empty element at position
  • Missing closing bracket for array
  • Missing closing bracket for object
  • Unterminated string at position
  • Missing property name/value delimiter (:) at position
  • Missing property value at position
  • Missing fractional part of a floating-point number at position
  • Exponent of the number is not integer at position
  • Unquoted property name at position
  • Control character encountered at position
  • Unrecognized escape sequence at position
  • Invalid UNICODE escape sequence at position
  • Unescaped symbol at position
  • Empty property name at position
  • Expected closing bracket or comma at position