What is JSON

winston

SuperObject
What is JSON ?

JSON (JavaScript Object Notation) is a lightweight data-interchange format.
It is easy for humans to read and write.
It is easy for machines to parse and generate.
It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999.
JSON is a text format that is completely language independent but uses conventions that are familiar to programmers.
These properties make JSON an ideal data-interchange language.
You can get more informations on json.org.

1. {
2.   "name": "Henri Gourvest", /* this is a comment */
3.   "vip": true,
4.   "telephones": ["000000000", "111111111111"],
5.   "age": 33,
6.   "size": 1.83,
7.   "adresses": [
8.     {
9.       "adress": "blabla",
10.       "city": "Metz",
11.       "pc": 57000
12.     },
13.     {
14.       "adress": "blabla",
15.       "city": "Nantes",
16.       "pc": 44000
17.     }
18.   ]
19. }

复制代码

Parsing a JSON data structure

1. var
2.   obj: ISuperObject;
3. begin
4.   obj := SO('{"foo": true}');
5.   obj := TSuperObject.ParseString('{"foo": true}');
6.   obj := TSuperObject.ParseStream(stream);
7.   obj := TSuperObject.ParseFile(FileName);
8. end;

复制代码

Accessing data

There isn't individual datastructure for each supported data types.
They are all an object: the ISuperObject.

  val := obj.AsObject.S['foo']; // get a

1. val := obj.AsString;
2.   val := obj.AsInteger;
3.   val := obj.AsBoolean;
4.   val := obj.AsDouble;
5.   val := obj.AsArray;
6.   val := obj.AsObject;
7.   val := obj.AsMethod;

复制代码

How to read a property value of an object ?

  // the advanced way

1. string
2.   val := obj.AsObject.I['foo']; // get an Int64
3.   val := obj.AsObject.B['foo']; // get a Boolean
4.   val := obj.AsObject.D['foo']; // get a Double
5.   val := obj.AsObject.O['foo']; // get an Object (default)
6.   val := obj.AsObject.M['foo']; // get a Method
7.   val := obj.AsObject.N['foo']; // get a null object

复制代码

How to read a value from an array ?

1.   val := obj.AsArray.S[0]; // get a string
2.   val := obj.AsArray.I[0]; // get an Int64
3.   val := obj.AsArray.B[0]; // get a Boolean
4.   val := obj.AsArray.D[0]; // get a Double
5.   val := obj.AsArray.O[0]; // get an Object (default)
6.   val := obj.AsArray.M[0]; // get a Method
7.   val := obj.AsArray.N[0]; // get a null object

复制代码

Using paths

  obj['foo']; // get a property

Using paths is a very productive method to find an object when you know where is it.
This is some usage cases:

  obj := so('{"index": 1, "items": ["item 1", "item 2", "item 3"]}');

1.   obj['123']; // get an item array
2.   obj['foo.list']; // get a property from an object
3.   obj['foo[123]']; // get an item array from an object
4.   obj['foo(1,2,3)']; // call a method
5.   obj['foo[]'] := value; // add an item array

复制代码

you also can encapsulate paths:

  obj := so('{"index": 1, "items": ["item 1", "item 2", "item 3"]}');

1.   obj['items[index]'] // return "item 2"

复制代码

or recreate a new data structure from another:

1.   obj['{"item": items[index], "index": index}'] // return {"item": "item 2", "index": 1}

复制代码

Browsing data structureUsing Delphi enumerator.

var

Using Delphi enumerator you can browse item's array or property's object value in the same maner.

var

1.   item: ISuperObject;
2. begin
3.   for item in obj['items'] do ...

复制代码

you can also browse the keys and values of an object like this:

var

1.   item: TSuperAvlEntry;
2. begin
3.   for item in obj.AsObject do ...
4.   begin
5.     item.Name;
6.     item.Value;
7.   end;

复制代码

Browsing object properties without enumerator

var

1.   item: TSuperObjectIter;
2. begin
3.   if ObjectFindFirst(obj, item) then
4.   repeat
5.     item.key;
6.     item.val;
7.   until not ObjectFindNext(item);
8.   ObjectFindClose(item);

复制代码

Browsing array items without enumerator

type

1.   item: Integer;
2. begin
3.   for item := 0 to obj.AsArray.Length - 1 do
4.     obj.AsArray[item]

复制代码

RTTI & marshalling in Delphi 2010

  obj.AsJSon(options);

1.   TData = record
2.     str: string;
3.     int: Integer;
4.     bool: Boolean;
5.     flt: Double;
6.   end;
7. var
8.   ctx: TSuperRttiContext;
9.   data: TData;
10.   obj: ISuperObject;
11. begin
12.   ctx := TSuperRttiContext.Create;
13.   try
14.     data := ctx.AsType<TData>(SO('{str: "foo", int: 123, bool: true, flt: 1.23}'));
15.     obj := ctx.AsJson<TData>(data);
16.   finally
17.     ctx.Free;
18.   end;
19. end;

复制代码

Saving data

  SO(['prop1', true, 'prop2', 123

1.   obj.SaveTo(stream);
2.   obj.SaveTo(filename);

复制代码

Helpers

1. ]); // return an object {"prop1": true, "prop2": 123}
2.   SA([true, 123]); // return an array [true, 123]

复制代码

Non canonical formsThe SuperObject is able to parse non canonical forms.

1. // unquoted identifiers
2. SO('{foo: true}');
3. // unescaped or unquoted strings
4. SO('{собственность: bla bla bla}');
5. // excadecimal
6. SO('{foo: \xFF}');

复制代码