Question

我正在从Map数据动态创建对象，填充字段以匹配键名。在父节点上定义字段时会出现问题，尝试在父字段上设置值会产生错误：

No static setter 'name' declared in class 'Skill'.

  NoSuchMethodError : method not found: 'name'

代码：

class Resource {
  String name;
  String description;

  Resource.map(Map data)
  {
    ClassMirror c = reflectClass(runtimeType);
    ClassMirror thisType = c;
    while(c != null)
    {
      for (var k in c.declarations.keys) {
        print('${MirrorSystem.getName(k)} : ${data[MirrorSystem.getName(k)]}');
        if(data[MirrorSystem.getName(k)] != null)
        {
          thisType.setField(k, data[MirrorSystem.getName(k)]);        
        }
      }
      c = c.superclass;
    }
  }
}

class Skill extends Resource
{
  Skill.map(data) : super.map(data);
}

Answer 1

您应该使用ObjectMirror在对象上设置字段。您的代码尝试在ClassMirror上设置一个字段，该字段尝试定义静态变量。

class Resource {
  String name;
  String description;

  Resource.map(Map data)
  {
    ObjectMirror o = reflect(this);  // added
    ClassMirror c = reflectClass(runtimeType);
    ClassMirror thisType = c;
    while(c != null)
    {
      for (var k in c.declarations.keys) {
        print('${MirrorSystem.getName(k)} : ${data[MirrorSystem.getName(k)]}');
        if(data[MirrorSystem.getName(k)] != null)
        {
          // replace "thisType" with "o"
          o.setField(k, data[MirrorSystem.getName(k)]);
        }
      }
      c = c.superclass;
    }
  }
}

class Skill extends Resource
{
  Skill.map(data) : super.map(data);
}

Answer 2

Dart中不会继承静态方法/字段这里已经有一些关于这种行为的讨论了您可以查看此问题的答案in Dart, using Mirrors, how would you call a class's static method from an instance of the class?

如果您尝试访问的方法/字段不是静态的，请提供更多代码（您要反映的类/对象）

Answer 3

此示例更安全，因为它执行其他操作：

仅查询指定的类型成员。
执行类型兼容性检查。
尝试转换值。

import 'package:reflection/reflection.dart';

class ObjectFiller {
  static void fill(Object obj, Map map) {
    var ti = typeInfo(obj.runtimeType);
    // Query only specified type members
    for(VariableInfo vi in ti.getVariables(BindingFlags.PUBLIC |
      BindingFlags.INSTANCE).values) {
      var name = SymbolHelper.getName(vi.simpleName);
      if(map.containsKey(name)) {
        var value = map[name];
        // Perform type compatibility checks.
        if(typeInfo(value.runtimeType).isAssignableFrom(vi.type)) {
          vi.setValue(obj, value);
        } else {
          // Try convert values.
          if(value is String) {
            if(typeInfo(int).isAssignableFrom(vi.type)) {
              try {
                vi.setValue(obj, int.parse(value));
              } catch(e) {
              }
            }
          }
        }
      }
    }
  }
}

void main() {
  var objects = [];
  // null object
  objects.add([null, {"foo" : 41}]);
  // Zebra object (without one front tooth)
  // Slipped, fell, woke up - one tooth missing
  objects.add([new Zebra(), {"numberOfTeeth" : "43", "numberOfStripes" : 30}]);
  // Zebra object
  objects.add([new Zebra(), {"numberOfTeeth" : 44, "numberOfStripes" : 40}]);
  // Filling  objects
  for(var object in objects) {
    ObjectFiller.fill(object[0], object[1]);
  }
  // Dumping objects (full)
  for(var object in objects) {
    var obj = object[0];
    print("Full dump of ${obj}");
    print(objectToMap(obj));
    print("---------------------------");
  }
  // Dumping objects (short)
  for(var object in objects) {
    var obj = object[0];
    print("Short dump of ${obj}");
    print(objectToMap(obj, true));
    print("---------------------------");
  }
}

Map objectToMap(Object obj, [bool declaredOnly = false]) {
  var map = {};
  if(obj == null) {
    return map;
  }

  var flags = BindingFlags.PUBLIC | BindingFlags.INSTANCE;
  if(declaredOnly) {
    flags |= BindingFlags.DECLARED_ONLY;
  }

  var ti = typeInfo(obj.runtimeType);
  for(VariableInfo vi in ti.getVariables(flags).values) {
    var name = SymbolHelper.getName(vi.simpleName);
    map[name] = vi.getValue(obj);
  }

  for(PropertyInfo pi in ti.getProperties(flags).values) {
    if(pi.isGetter) {
      var name = SymbolHelper.getName(pi.simpleName);
      map[name] = pi.getValue(obj);
    }
  }

  return map;
}

abstract class Animal {
  static String unusedInAnimal;

  int numberOfTeeth = 0;

  String get family;
}

class Zebra extends Animal {
  static String unusedInZebra;

  int numberOfStripes = 0;

  String get family => "Equidae";
}

Full dump of null
{}
---------------------------
Full dump of Instance of 'Zebra'
{numberOfTeeth: 43, numberOfStripes: 30, hashCode: 970552119, runtimeType: Zebra, family: Equidae}
---------------------------
Full dump of Instance of 'Zebra'
{numberOfTeeth: 44, numberOfStripes: 40, hashCode: 1024653070, runtimeType: Zebra, family: Equidae}
---------------------------
Short dump of null
{}
---------------------------
Short dump of Instance of 'Zebra'
{numberOfStripes: 30, family: Equidae}
---------------------------
Short dump of Instance of 'Zebra'
{numberOfStripes: 40, family: Equidae}
---------------------------

在Dart中动态填充父字段

3 个答案: