mwf_utils
Other utilities.
prepare_object()
template <class T>
static inline std::unique_ptr<T>& prepare_object(std::unique_ptr<T>& spobj, bool b_construct_if_null = true) {
if (!spobj && b_construct_if_null) {
spobj.reset(new T());
}
return spobj;
}
This function references an object of the smart pointer std::unique_ptr<>. If the object has not been constructed, it is constructed using new T().
get_value_if()
// When getting a value from a function and proceeding with a process using that value
int v = some_func();
if (v != -1) {
// Do something with the value of v
printf("%d", v);
}
// Rewrite as follows
if (auto x = get_value_if::ne(some_func(), -1)) {
printf("%d", x.value());
}
As shown in the example above, this is a utility class for writing code that uses a function’s return value under a certain condition, by using a variable declaration within an if statement.
In the example above, get_value_if::ne() is used. The first parameter is a function call that returns a value, and the second parameter specifies the value for comparison. In this case, the if block is evaluated only when the return value of some_func() is not -1. The types of the first and second parameters must be the same.
The following comparison expressions can be used: eq, ne, lt, le, gt, ge.
get_value_if::xx() (T is a type) | Condition | |
|---|---|---|
eq(T lhs, const T rhs) | (lhs == rhs) | Returns true if the values are the same. |
ne (T lhs, const T rhs) | (lhs != rhs) | Returns true if the values are different. |
lt (T lhs, const T rhs) | (lhs < rhs) | Compares values, returns true if the value is smaller. |
le (T lhs, const T rhs) | (lhs <= rhs) | Compares values, returns true if the value is less than or equal to. |
gt (T lhs, const T rhs) | (lhs > rhs) | Compares values, returns true if the value is larger. |
ge (T lhs, const T rhs) | (lhs >= rhs) | Compares values, returns true if the value is greater than or equal to. |
Note: T indicates a type (a type parameter in a template construct).