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 Employee {
  name :: STRING
  salary :: DOUBLE
  department :: STRING
  
  def Employee(name_, salary_, dept_) { 
    name = name_
    salary = salary_
    department = dept_
  }
  
  def updateInfo(newSalary,newDepartment) {
    salary = newSalary
    department = newDepartment
    return "Salary updated to $" + string(salary) + ", and department updated to " + department
  }
  
  def getInfo(includeDetails) {
    return iif(includeDetails, 
               name + " - " + department + " - $" + string(salary),
               name + " - " + department)
  }
}
emp = Employee("Alice", 50000.0, "Department1")

// Use objCall
objCall(emp, "getInfo", true)
// Use unifiedObjCall
unifiedObjCall(emp, "updateInfo", (55000.0,"Department2"))
// Use makeObjCall
makeObjCall(emp, "updateInfo", 60000.0,"Department3").eval()
// Use makeUnifiedObjCall
makeUnifiedObjCall(emp, "updateInfo", (65000.0,"Department4")).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.