sc::prefixkeyval(3)

NAME

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

SYNOPSIS

#include <keyval.h>
Inherits sc::KeyVal.
Public Member Functions
void errortrace (std::ostream &fp=ExEnv::err0())
    Write a message to fp describing the error.
void dump (std::ostream &fp=ExEnv::err0())
    Write a message to fp describing the error.
Constructors.
Construct a PrefixKeyVal, using the given prefix and indices.
    PrefixKeyVal (const Ref< KeyVal > &, int i)
    PrefixKeyVal (const Ref< KeyVal > &, int i, int j)
    PrefixKeyVal (const Ref< KeyVal > &, int i, int j, int k)
    PrefixKeyVal (const Ref< KeyVal > &, int i, int j, int k, int l)
    PrefixKeyVal (const Ref< KeyVal > &, const char *prefix)
    PrefixKeyVal (const Ref< KeyVal > &, const char *prefix, int i)
    PrefixKeyVal (const Ref< KeyVal > &, const char *prefix, int i, int
        j)
    PrefixKeyVal (const Ref< KeyVal > &, const char *prefix, int i, int
        j, int k)
    PrefixKeyVal (const Ref< KeyVal > &, const char *prefix, int i, int
        j, int k, int l)

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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Version 2.3.1 15 Mar 2008 sc::PrefixKeyVal(3)