If I needed to initialize only a few select values of a C++ struct, would this be correct:
struct foo {
foo() : a(true), b(true) {}
bool a;
bool b;
bool c;
} bar;
Am I correct to assume I would end up with one struct
item called bar
with elements bar.a = true
, bar.b = true
and an undefined bar.c
?
This question is related to
c++
You can do it by using a constructor, like this:
struct Date
{
int day;
int month;
int year;
Date()
{
day=0;
month=0;
year=0;
}
};
or like this:
struct Date
{
int day;
int month;
int year;
Date():day(0),
month(0),
year(0){}
};
In your case bar.c is undefined,and its value depends on the compiler (while a and b were set to true).
An explicit default initialization can help:
struct foo {
bool a {};
bool b {};
bool c {};
} bar;
Behavior bool a {}
is same as bool b = bool();
and return false
.
You don't even need to define a constructor
struct foo {
bool a = true;
bool b = true;
bool c;
} bar;
To clarify: these are called brace-or-equal-initializers (because you may also use brace initialization instead of equal sign). This is not only for aggregates: you can use this in normal class definitions. This was added in C++11.
Source: Stackoverflow.com