Unified Initialization with {}

The initialization of variables became uniform in C++11. For unified initialization, we need the {} brackets.

{} initialization is always applicable.

Direct initialization

Variables can be declared directly without the assignment operator:

std::string str{"my String"};
int i{2011};

Copy initialization

{} also supports copy initialization with the = operator:

std::string str = {"my String"};
int i = {2011};

The difference is that direct initialization directly calls the constructor of the type, whereas, in copy initialization, the value is created and implicitly converted into the type.

Preventing narrowing

Narrowing, or more precisely narrowing conversion, is an implicit conversion of arithmetic values from one type to another. This can cause a loss of accuracy, which can be extremely dangerous.

The following example shows the issue with the classical way of initializing fundamental types.

The compiler presents a warning, yet the implicit conversions are performed nonetheless, resulting in data loss.

It doesn’t matter whether we use direct initialization or assignment: