Commit f0901aec authored by Blake Matheny's avatar Blake Matheny Committed by Andrii Grynenko

get_or_throw and get_optional

Summary:
Adds get_or_throw map helper (get a value, or throw with the specified
exception type) and get_optional (get an Optional<Value>). This is a folly
backport of some util helpers in experimental.

Test Plan: Unit tests

Reviewed By: wez@fb.com

Subscribers: folly-diffs@, yfeldblum, chalfant

FB internal diff: D2029802

Tasks: 4332480

Signature: t1:2029802:1430280249:3efbb2fb9394e31b3fbe6d5bd209d12ebb7ed587
parent f3e177a5
...@@ -17,6 +17,9 @@ ...@@ -17,6 +17,9 @@
#ifndef FOLLY_MAPUTIL_H_ #ifndef FOLLY_MAPUTIL_H_
#define FOLLY_MAPUTIL_H_ #define FOLLY_MAPUTIL_H_
#include <folly/Conv.h>
#include <folly/Optional.h>
namespace folly { namespace folly {
/** /**
...@@ -32,6 +35,36 @@ typename Map::mapped_type get_default( ...@@ -32,6 +35,36 @@ typename Map::mapped_type get_default(
return (pos != map.end() ? pos->second : dflt); return (pos != map.end() ? pos->second : dflt);
} }
/**
* Given a map and a key, return the value corresponding to the key in the map,
* or throw an exception of the specified type.
*/
template <class E = std::out_of_range, class Map>
typename Map::mapped_type get_or_throw(
const Map& map, const typename Map::key_type& key,
const std::string& exceptionStrPrefix = std::string()) {
auto pos = map.find(key);
if (pos != map.end()) {
return pos->second;
}
throw E(folly::to<std::string>(exceptionStrPrefix, key));
}
/**
* Given a map and a key, return a Optional<V> if the key exists and None if the
* key does not exist in the map.
*/
template <class Map>
folly::Optional<typename Map::mapped_type> get_optional(
const Map& map, const typename Map::key_type& key) {
auto pos = map.find(key);
if (pos != map.end()) {
return folly::Optional<typename Map::mapped_type>(pos->second);
} else {
return folly::none;
}
}
/** /**
* Given a map and a key, return a reference to the value corresponding to the * Given a map and a key, return a reference to the value corresponding to the
* key in the map, or the given default reference if the key doesn't exist in * key in the map, or the given default reference if the key doesn't exist in
......
...@@ -29,6 +29,28 @@ TEST(MapUtil, get_default) { ...@@ -29,6 +29,28 @@ TEST(MapUtil, get_default) {
EXPECT_EQ(0, get_default(m, 3)); EXPECT_EQ(0, get_default(m, 3));
} }
TEST(MapUtil, get_or_throw) {
std::map<int, int> m;
m[1] = 2;
EXPECT_EQ(2, get_or_throw(m, 1));
EXPECT_THROW(get_or_throw(m, 2), std::out_of_range);
}
TEST(MapUtil, get_or_throw_specified) {
std::map<int, int> m;
m[1] = 2;
EXPECT_EQ(2, get_or_throw<std::runtime_error>(m, 1));
EXPECT_THROW(get_or_throw<std::runtime_error>(m, 2), std::runtime_error);
}
TEST(MapUtil, get_optional) {
std::map<int, int> m;
m[1] = 2;
EXPECT_TRUE(get_optional(m, 1));
EXPECT_EQ(2, get_optional(m, 1).value());
EXPECT_FALSE(get_optional(m, 2));
}
TEST(MapUtil, get_ref_default) { TEST(MapUtil, get_ref_default) {
std::map<int, int> m; std::map<int, int> m;
m[1] = 2; m[1] = 2;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment