委托 抽象方法

dynamic delegate(
  1. Invocation invocation
)

在此 ObjectMirror 的反射对象上执行 invocation

相当于

if (invocation.isGetter) {
  return this.getField(invocation.memberName).reflectee;
} else if (invocation.isSetter) {
  return this.setField(invocation.memberName,
                       invocation.positionalArguments[0]).reflectee;
} else {
  return this.invoke(invocation.memberName,
                     invocation.positionalArguments,
                     invocation.namedArguments).reflectee;
}

实现

delegate(Invocation invocation);