Utility Functions

Metaprogramming

DolphinDB supports generating metacode for method calls defined within classes using the following functions:

• objCall(obj, methodName, args...)

• unifiedObjCall(obj, methodName, args)

• makeObjCall(obj, methodName, args...)

• makeUnifiedObjCall(obj, methodName, args)

where

• obj is the object.

• methodName is a string representing the method name.

• args... are the parameters passed to the method.

Examples

Use makeObjCall to create metacode for OOP method calls:

class Person {
  name :: STRING
  age :: INT
  def Person(name_, age_) { 
    name = name_
    age = age_
  }
  def setName(newName) {
    name = newName
  }
  def getName(year, gender) {
    if (year < 2020)
      return year
    else
      return name
  }
}
a = Person("Harrison", 20)
f = a.getName{2015}
f(true)
// Use objCall
objCall(a, "getName", 2015, true)
// Use unifiedObjCall
unifiedObjCall(a, "getName", (2015, true))
// Use makeObjCall
makeObjCall(a, "getName", 2015, true).eval()
// Use makeUnifiedObjCall
makeUnifiedObjCall(a, "getName", (2015, true)).eval()

Other Functions

• isInstanceOf(obj, cls): Checks if an object is an instance of a specific class or its derived class, returning a Boolean value.

  class B {
    def B() {}
  }
  class D : B {
    def D() {}
  }
  class A {
    def A() {}
  }
  d = D()
  isInstanceOf(d, D)  // true
  isInstanceOf(d, B)  // true
  isInstanceOf(d, A)  // false

• setAttr(obj, attrName, value): Sets or modifies the attributes of an object obj. For example, setAttr(obj, `alpha, 16), or obj.setAttr(`alpha, 16).

These utility functions enable flexible and dynamic manipulation of class instances and their methods, enhancing the power of object-oriented programming in DolphinDB.