Explicit keywords in C + +

The explicit keyword is in C + + to prevent an implicit conversion

(1)

Explicit

This keyword can only work on the user's own defined object, not the default constructor
This keyword can only decorate constructors. And the constructor parameter can only have one:

(2) When to use explicit

When we do not want to use the automatic type conversion, in fact, the standard library a lot of constructors are explicit

such as vectors <int> Ivec (10); This definition looks at a glance

cannot be written as vector <int> ivec=10;//This definition makes the programmer wonder

(3) when not to explicit

When we need an implicit conversion,

For example, a constructor for a string class

String (const char*);

This is defined as the benefit of the compiler automatically helping us to convert when implicit conversions are required, and the string in the standard library is a good proof.

Specifically:

We can do this by string str= "HelloWorld";//Call constructor directly

String str= "Hello" +str+ "world";

Call the overloaded + action symbol, which is equivalent to:
String temp ("Hello"); Call constructor

String Str=temp+str;

String T ("World");//Call constructor

String str=str+t;

It is useful to understand implicit conversions when we write our own classes, especially when manipulating memory classes.

Explicit keywords in C + +