bdlb_pairutil

Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Basic Usage

Purpose

Provide a function that creates a pair of references.

Classes

• bdlb::PairUtil: namespace for the bdlb::PairUtil::tie function

Description

This component provides the class bdlb::PairUtil, which has a single static member function, tie, which is intended to be used in place of bsl::tie when the right-hand side of the assignment is a bsl::pair.

Usage

This section illustrates intended use of this component.

Example 1: Basic Usage

Suppose we need to implement a function that takes a bsl::map and stores into out-parameters the key and value corresponding to the first entry in the map. Using bsl::maps container interface, we can obtain a reference to a bsl::pair of the key and value. We can then use bdlb::PairUtil::tie to assign from both the key and value in a single expression:

/// Load into the specified `key` and the specified `value` the key and
/// value for the first entry in the specified `map` and return `true`,
/// or else fail by storing 0 and an empty string and return `false`
/// when `map` is empty.
bool getFirst(int                              *key,
              bsl::string                      *value,
              const bsl::map<int, bsl::string>& map)
{
    if (map.empty()) {
        *key = 0;
        value->clear();
        return false;                                             // RETURN
    }
    bdlb::PairUtil::tie(*key, *value) = *map.begin();
    return true;
}
 
void usageExample()
{
    bsl::map<int, bsl::string> map;
    map[30782530] = "bbi10";
 
    int         uuid;
    bsl::string username;
 
    bool result = getFirst(&uuid, &username, map);
    assert(result);
    assert(30782530 == uuid);
    assert("bbi10"  == username);
}