uniform initialization c++11

There were two initialization before c++11:

1. Using parentheses
2. Using assignment operator

Now c++11, introduced new initialization that is “Uniform initialization“, which mean one common way of intialization for all data types even user defined and its syntax is braces{}.

Using “Uniform initialization” we can initialize all data type, please check below code:

Note: We can use “Uniform initialization” for user defined Object using std::initializer_list but we need define constructor to handle this request, it will be handled by initializer-list constructor.

//Interger
int i_val01{1};
std::cout<<"i_val01:"<<i_val01<<std::endl;

//Float
float f_val01{1.1};
std::cout<<"f_val01:"<<f_val01<<std::endl;

//String
std::string s_val01{"test"};
std::cout<<"s_val01:"<<s_val01<<std::endl;

//Vector
std::vector<int> v_vec{1, 2, 3};
std::cout<<"v_vec[0]:"<<v_vec[0]<<std::endl;

//User defined Object, we can initialize with {} but
//we need define constructor to handle this request
//This is NOT good option for object creation
//I will explain in other topic
test obj{1};
std::cout<<"class member value:"<<obj.getVal()<<std::endl;

//Initialization with empty
int i_val02{};
std::cout<<"i_val02:"<<i_val02<<std::endl;

//Pointer initialized with nullptr
int* ip_Val{};
std::cout<<"ip_val:"<<ip_Val<<std::endl;

Advantages:

• Empty braces initialize the variable with proper type so we can get ride from uninitialized variable problem,please check above code.
• Stop implicit or automatic conversion like float is converted to int automatically, please check below error.

 //int i_val04{1.1};
//std::cout<<"i_val04:"<<i_val04<<std::endl;
//error: narrowing conversion of ‘1.1000000000000001e+0’ from ‘double’ to ‘int’

Complete source code with example:

#include<iostream>
#include<vector>

class test
{
int m_i;
public:
test(const std::initializer_list<int>& list)
{

for(const auto& ele : list)
{
m_i = ele;
}
}
int getVal(){return m_i;}
};

int main()
{
std::cout<<"Uniform Initialization"<<std::endl;

//Interger
int i_val01{1};
std::cout<<"i_val01:"<<i_val01<<std::endl;

//Float
float f_val01{1.1};
std::cout<<"f_val01:"<<f_val01<<std::endl;

//String
std::string s_val01{"test"};
std::cout<<"s_val01:"<<s_val01<<std::endl;

//Vector
std::vector<int> v_vec{1, 2, 3};
std::cout<<"v_vec[0]:"<<v_vec[0]<<std::endl;

//User defined Object, we can initialize with {} but
//we need define constructor to handle this request
test obj{1};
std::cout<<"class member value:"<<obj.getVal()<<std::endl;

//Initialization with empty
int i_val02{};
std::cout<<"i_val02:"<<i_val02<<std::endl;

//Pointer initialized with nullptr
int* ip_Val{};
std::cout<<"ip_val:"<<ip_Val<<std::endl;

//int i_val03{2, 2 };
//std::cout<<"i_val03:"<<i_val03<<std::endl;
//error: scalar object ‘i_val03’ requires one element in initializer

//int i_val04{1.1};
//std::cout<<"i_val04:"<<i_val04<<std::endl;
//error: narrowing conversion of ‘1.1000000000000001e+0’ from ‘double’ to ‘int’

return 0;
}

Output:

Uniform Initialization
i_val01:1
f_val01:1.1
s_val01:test
v_vec[0]:1
class member value:1
i_val02:0
ip_val:0