用大括号或圆括号初始化成员变量

Question

When initializing member variables in a constructor you can do it in these two different ways, using braces or parentheses:

class some_class {

some_class(): foo{<value>}, bar(<value>) {}

T foo;
T bar;
};

Is there a functional difference between these two initialization methods, and if so, which one should I opt to use?

Answer 1

Depends of T . for example with [T = std::vector<int>] ,

foo{4, 5} is a container with 2 items (4 and 5),

whereas foo(42, 0) is a container with 42 items (with value 0).

You might read initialization which explains the different kind of initializations for further detail...