Question

为我的生活添加一些理智，为Dart的instantiate()库寻找mirror函数作为语法糖：instantiate( class|type|instance, argArray )

class Klass {
  int i1;
  Klass( int i1 ) {
    this.i1 = (i1 is int) ? i1 : 0;
  }
}
type ktype = Klass;
Klass kinstance = new Klass( 5 );

Klass test1 = instantiate( Klass, [5] );
Klass test2 = instantiate( ktype, [5] );
Klass test3 = instantiate( kinstance, [5] );

目前我与mirrors的90％的互动都会被这一功能所覆盖。目前盲目地削减和复制出纯粹的愚蠢。当然比我聪明的人已经做到了！

所有场合都是instantiate( type, [constructor, positional, named] )：

构造函数，位置和命名的参数都是可选的
类型可以是Type，实例化类型或类型
构造函数：例如，new Map.from（...） - 'from'是构造函数，'from'或#from
位置：列表中的位置参数
named：在Map中命名参数，键可以是'key'或#key

dynamic instantiate( dynamic v_type, [dynamic v_constructorName, List v_positional, Map v_named] ) {
  Type type =
    ( _type is Type ) ? v_type
    : (v_type is String ) ? str2Type( v_type )
    : reflect(v_type).type.reflectedType;
  Map v_named2 =
    (v_named is Map) ? v_named
    : (v_positional is Map) ? v_positional
    : (v_constructorName is Map) ? v_constructorName
    : {};
  Map named = {};
  v_named2.keys.forEach( (k) => named[(k is Symbol)?k:new Symbol(k)] = v_named2[k] );
  List positional =
    (v_positional is List) ? v_positional
    : (v_constructorName is List) ? v_constructorName : [];
  Symbol constructorName =
    (v_constructorName is Symbol) ? v_constructorName
    : (v_constructorName is String) ? Symbol(v_constructorName)
    : const Symbol('');
  return reflectClass(type).newInstance(constructorName, positional, named).reflectee;
}

Answer 1

import 'dart:mirrors';

void main() {
  Type ktype = Klass;
  Klass kinstance = new Klass( 5 );
  // Constructor name
  var ctor = const Symbol("");

  Klass test1 = instantiate(Klass, ctor, [1]);
  Klass test2 = instantiate(ktype, ctor, [2]);
  Klass test3 = instantiate(reflect(kinstance).type.reflectedType, ctor, [3]);
  Klass test4 = instantiate(Klass, #fromString, ["4"]);

  print(test1.i1);
  print(test2.i1);
  print(test3.i1);
  print(test4.i1);
}

dynamic instantiate(Type type, Symbol constructorName, List positional, [Map named]) {
  return reflectClass(type).newInstance(constructorName, positional, named).reflectee;
}

class Klass {
  int i1;
  Klass( int i1 ) {
    this.i1 = (i1 is int) ? i1 : 0;
  }

  Klass.fromString(String i) {
    i1 = int.parse(i, onError : (s) => i1 = 0);
  }
}

输出：

需要Dart镜像instantiate（）函数

1 个答案: