66///
77// #docregion idiomatic-constructor
88class Point {
9- double x = 0 ;
10- double y = 0 ;
9+ // Initializer list of variables and values
10+ double x = 2.0 ;
11+ double y = 2.0 ;
1112
1213 // Generative constructor with initializing formal parameters:
1314 Point (this .x, this .y);
@@ -34,3 +35,66 @@ class Point {
3435// #docregion idiomatic-constructor
3536}
3637// #enddocregion idiomatic-constructor
38+
39+ // #docregion initialize-declaration
40+ class PointA {
41+ double x = 1.0 ;
42+ double y = 2.0 ;
43+
44+ // The implicit default constructor sets these variables to (1.0,2.0)
45+ // PointA();
46+
47+ @override
48+ String toString () {
49+ return 'PointA($x ,$y )' ;
50+ }
51+ }
52+ // #enddocregion initialize-declaration
53+
54+ // #docregion initialize-formal
55+ class PointB {
56+ final double x;
57+ final double y;
58+
59+ // Sets the x and y instance variables
60+ // before the constructor body runs.
61+ PointB (this .x, this .y);
62+
63+ // Initializing formal parameters can also be optional.
64+ PointB .optional ([this .x = 0.0 , this .y = 0.0 ]);
65+ }
66+ // #enddocregion initialize-formal
67+
68+ // #docregion initialize-named
69+ class PointC {
70+ double x; // must be set in constructor
71+ double y; // must be set in constructor
72+
73+ // Generative constructor with initializing formal parameters
74+ // with default values
75+ PointC .named ({this .x = 1.0 , this .y = 1.0 });
76+
77+ @override
78+ String toString () {
79+ return 'PointC.named($x ,$y )' ;
80+ }
81+ }
82+
83+ // Constructor using named variables.
84+ final pointC = PointC .named (x: 2.0 , y: 2.0 );
85+ // #enddocregion initialize-named
86+
87+ // #docregion initialize-null
88+ class PointD {
89+ double ? x; // null if not set in constructor
90+ double ? y; // null if not set in constructor
91+
92+ // Generative constructor with initializing formal parameters
93+ PointD (this .x, this .y);
94+
95+ @override
96+ String toString () {
97+ return 'PointD($x ,$y )' ;
98+ }
99+ }
100+ // #enddocregion initialize-null
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