extended class syntax: what changed

Revision 0 to 1. Removed lines have a minus sign; added lines have a plus sign.

Title: extended class syntax

New		Line
1	+	### Static fields, static properties, regular fields and regular properties
2	+
3	+	``` pascal
4	+	type
5	+	TSomeClass = class
6	+	private
7	+	type
8	+	TSomeType = type integer; // an internal type
9	+	class var
10	+	FSomeClassVar: TSomeType; // class variable belongs to a class, not an instance
11	+	var
12	+	FSomeIntanceVar: TSomeType; // instance variable belongs to instance. it is a usual field
13	+	class procedure SetSomeClassVar(const AValue: TSomeType); static;
14	+	public
15	+	class property SomeProperty: TSomeType read FSomeClassVar write SetSomeClassVar; // class property - belongs to a class
16	+	property SomeInstanceProp: TSomeType read FSomeIntanceVar;
17	+	end;
18	+
19	+	{ TSomeClass }
20	+
21	+	class procedure TSomeClass.SetSomeClassVar(const AValue: TSomeType);
22	+	begin
23	+	FSomeClassVar := AValue;
24	+	end;
25	+
26	+	var
27	+	SomeClass: TSomeClass;
28	+	begin
29	+	SomeClass.SomeProperty := 1;
30	+	WriteLn(SomeClass.SomeProperty);
31	+	end.
32	+	```
33	+
34	+	### Class constants
35	+
36	+	``` pascal
37	+	type
38	+	TSomeClass = class
39	+	strict private
40	+	const
41	+	PrivateConst = 1;
42	+	type
43	+	PrivateType = type Integer;
44	+	var
45	+	FPrivateField: PrivateType;
46	+	public
47	+	procedure DoSomething(Value: PrivateType = PrivateConst);
48	+	function ReturnSomething: PrivateType;
49	+	property SomeProp: PrivateType read FPrivateField write FPrivateField default PrivateConst;
50	+	end;
51	+
52	+	procedure TSomeClass.DoSomething(Value: PrivateType = PrivateConst);
53	+	begin
54	+	end;
55	+
56	+	function TSomeClass.ReturnSomething: PrivateType;
57	+	begin
58	+	Result := PrivateConst;
59	+	end;
60	+
61	+	begin
62	+	end.
63	+	```
64	+
65	+	### Nested classes
66	+
67	+	``` pascal
68	+	type
69	+	TSomeClass = class
70	+	strict private
71	+	type
72	+	TPrivateNestedClass = class
73	+	public
74	+	procedure DoSomething;
75	+	end;
76	+	public
77	+	type
78	+	TNestedClass = class
79	+	public
80	+	procedure DoSomething;
81	+	end;
82	+	class procedure Test; virtual;
83	+	end;
84	+
85	+	TDescendant = class(TSomeClass)
86	+	public
87	+	class procedure Test; override;
88	+	end;
89	+
90	+	procedure TSomeClass.TPrivateNestedClass.DoSomething;
91	+	begin
92	+	WriteLn('TSomeClass.TPrivateNestedClass.DoSomething: ok');
93	+	end;
94	+
95	+	procedure TSomeClass.TNestedClass.DoSomething;
96	+	begin
97	+	WriteLn('TSomeClass.TNestedClass.DoSomething: ok');
98	+	end;
99	+
100	+	class procedure TSomeClass.Test;
101	+	var
102	+	P: TPrivateNestedClass;
103	+	N: TNestedClass;
104	+	begin
105	+	P := TPrivateNestedClass.Create;
106	+	P.DoSomething;
107	+	P.Free;
108	+	N := TNestedClass.Create;
109	+	N.DoSomething;
110	+	N.Free;
111	+	end;
112	+
113	+	class procedure TDescendant.Test;
114	+	var
115	+	N: TNestedClass;
116	+	begin
117	+	N := TNestedClass.Create;
118	+	N.DoSomething;
119	+	N.Free;
120	+	end;
121	+
122	+	begin
123	+	TSomeClass.Test;
124	+	TDescendant.Test;
125	+	end.
126	+	```
127	+
128	+	---
129	+	From the Free Pascal wiki, page "extended class syntax", as it stood on 2020-02-14 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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