NAME

sc::PrefixKeyVal - PrefixKeyVal is a KeyVal that searches a different KeyVal using modified keys.

SYNOPSIS

#include <keyval.h>

Inherits sc::KeyVal.

Detailed Description

PrefixKeyVal is a KeyVal that searches a different KeyVal using modified keys.

This is convenient for reading keys grouped together with a common prefix. Consider the following code:

sc::Ref<sc::KeyVal> keyval = new sc::PrefixKeyVal('A',original_keyval);
int r = keyval->intvalue('x');

This code will assign to r the value associated with 'x' in keyval. keyval will search for 'x' by searching for 'A::x' in original_keyval.

This class is important for implementing constructors that take KeyVal arguments. When an object is being constructed from a KeyVal, it may contain another object that must be constructed from a KeyVal. In order to let the sub-object read the correct keywords from the KeyVal, without knowledge of the containing objects keyword prefix, a PrefixKeyVal can be constructed. For example, the code

class A: public DescribedClass {


   double f0_;


  public:


   A(const Ref<KeyVal> &keyval): f0_(keyval->doublevalue("f0")) {}
}
class B: public DescribedClass {


   double f1_;


   Ref<A> a_;


  public:


   B(const Ref<KeyVal> &keyval):


     f1_(keyval->doublevalue("f1")),


     a_(new PrefixKeyVal(keyval,"a"))


   {}
};

can be used to read ParsedKeyVal input that looks like

b<B>: (


  f1 = 1.0


  a<A>: (


    f0 = 2.0


  )
)

Author

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