reflectionchapel

How to access class or record field with the name of the field as a string?

Say you have a record or class:

record R {
  var value: int;
}

How can I access the field value by using the string "value"?

For example, in Python, you can access fields using the getattr built-in:

class C:
    def __init__(self, val):
        self.value = val

c = C(2)

print(getattr(c, 'value')) # prints 2

What would this look like in Chapel?

Solution

  • The Reflection module's getField() and getFieldRef() routines provide this capability. For example, the following program both reads and writes the field 'value' (TIO):

    use Reflection;

record R {
  var value: int;
}

var myR = new R(2);

writeln(getField(myR, "value"));  // print the field from 'myR' named "value"

getFieldRef(myR, "value") = 42;   // get a reference to the field from 'myR' named "value" and assign to it

writeln(myR);                     // print the resulting record