class JSON

Example

A class to parse text formatted in JSON format (Javascript Object Notation) into an internal object tree or array representation, manipulate this data, and than convert it back into JSON string format. JavaScript Object Notation is a minimal, readable format for structuring data. It is used primarily to transmit data between a server and web application.

Syntax

[<oRef>] = new JSON(<cString>)

<oRef>

A variable or property in which to store a reference to the newly created JSON object.

A reference to the string that the JSON object can be used to automatically parse the initial members or array objects.

Properties

Property	Default	Description
baseClassName	JSON	Identifies the object as an instance of the JSON class
className	(JSON)	Identifies the object as an instance of a custom class. When no custom class exists, defaults to baseClassName
member	null	a reference to the member object used to access the current member within a JSON object if a JSON object was contained in the parsed JSON text.
Method	Parameters	Description
getErrorOffset()		returns numeric offset into JSON string where error was encountered
getParseError()		returns string describing error (only available in English)
getParseErrorCode()		returns numeric error code
hasParseError()		returns True if last call to Parse() method encountered an error
parse()	<cMembers>	parses JSON string into internal JSON object or JSON array (depending on what is defined in the JSON string) if NOT using <Obj> = new JSON(cMembers) ... then use ... <Obj> = new JSON() <Obj>.parse(cMembers)
isArray()		returns True if the last parsed JSON text contained a JSON array
isEmpty()		returns True if the dBASE JSON() instance does not contain any JSON data
isObject()		returns True if the last parsed JSON text contained a JSON member object
stringify()		generates a JSON string from the current state of the contents of a JSON() object instance

Methods to use when isObject() returns True

Method	Parameters	Description
addMember()	<key string>, <value>	adds new member <key string> with value <value> to object
findMember()	<Key string>	searches for <key string>. returns True if found, otherwise, returns False. If found, sets member property to reference the found member
firstKey()		returns key string for first member of JSON object
firstMember()		sets member property to first member of object
hasMember()	<key string>	returns True if <key string> is found within the top level members of the object tree, otherwise, returns False.
lastMember()		sets member property to last member of object
memberCount()		returns the number of top level members within a JSON object, otherwise returns zero
nextKey()	<key string>	returns key string for next key string after <key string>. This does not set the member property. To do that you need to use findMember. For example... ... if J is JSON Object... cKey = j.firstKey() cKey2 = j.nextKey(cKey) j.findMember(cKey2)
nextMember()		sets member property to next member of object after the member currently referenced
previousMember()		sets member property to previous member of object before the member currently referenced
removeAllMembers()		removes all members from JSON object
removeMember()	<key string>	removes member <key string> from JSON object
setMemberValue()	<Key string>,<value>	changes <value> assigned to member <key string>

Methods to use when isArray() returns True

Method	Parameters	Description
append()	<value>	adds new element to JSON Array and assigns <value> to it
capacity()		returns number of elements that can fit in the memory currently allocated for a JSON Array
clear()		deletes all elements of JSON Array
delete()	nIndex	deletes array element <nindex> from JSON Array
getAt()	<nIndex>	returns value of array element specified by <nindex> (<nindex> is 1 based).
reserve()	<capacity>	allocates enough memory to hold <capacity> elements in a JSON Array
setAt()	<index>,<value>	returns True if able to assign <value> to array element <index>, otherwise, returns False.
size()		returns number of elements currently in the array

Description

There are two types of data that JSON can use. MEMBERS and ARRAYS.

Here are ways to create json objects...

MEMBERS

cMembers = '{"ID" : "1010", "Name" : "Marty", "Address" : "123 Main Street" }'

j = new JSON(cMembers)

cMembers = '{"ID" : "1010", "Name" : "Marty", "Address" : "123 Main Street" }'

j = new JSON()

j.parse(cMembers)

IMPORTANT NOTE: the string of members must be in this format ...

members all surrounded by single quotes surrounding curly braces with the members listed like so ..

'{ "MEMBER_ID" : "MEMBER VALUE" [, next member , ...] }'

each member must have it's ID and value delimited with double quotes.

Each ID and Value separated by a colon.

Each Member separated by a comma.

ARRAYS

a = '[1,2,3,4,5]'

//or

a = '["one","two","three",4]'

jsA = new json(a)

a = '["one","two","three",4]'

jsA.parse(a)

IMPORTANT NOTE: for an array you must use single quotes around square brackets around each array item separated by a comma.

SUBOBJECTS

you can have subobjects in a member json object.

You have to reference a subobject as a new member with this syntax ...

"<subObj>" : { "<member1>" : 123, "<member2>" : "value"}

values can be either numbers or characters. You can have many members.

Example....

//to findmember with sub object

var = '{"ID" : "1010", "Name" : "Marty", "Address" : "123 Main Street", "subObj" : { "prop1" : 123, "prop2" : 555} }'

js = new json()

js.parse(var)

?"find subObj",js.findmember("subObj")

?js.member.name,js.member.value

?"isObject",js.member.isobject()

?"find prop1",js.member.findmember("prop1")

?"name and value",js.member.member.name,js.member.member.value

?"find prop2",js.member.findmember("prop2")

?"name and value",js.member.member.name,js.member.member.value

In order to add a subobject to an existing JSON object, you must create a second json() object containing the content of the subobject.

Example...

s = '{"Sub1":"abc", "Sub2": "def"}'

o = new json(s)

sparent = '{"Memb1":"Val1", "Memb2":"Val2"}'

oparent = new json( sparent )

oparent.addmember("Memb3", o)