[017]string Class Usage precautions

Recently wrote a play, wrote a function like this:

void foo (conststring& iStr) {    for (int0; I < Istr.length (); + +i)        {string str = istr.at (i);    }}

The other business involved in the middle of the function, the problem is that after writing the above code, compile it.

At first glance, isn't that normal? Get a value in the ISTR and assign it to Str.

Actually, because usually we use the string with the habit, will habitually think it is the basic type, but, it is the class type Ah!

So, when we take the following actions:

string str = istr.at (i);

istr.at (i) returns a const char character, so when the instance is STR, it will find out if there is a copy constructor of the const char type in the string.

As a result, there is no way to copy the object, it is wrong.

void foo (conststring& iStr) {    for (int0; I < Istr.length (); + +i)        {constchar str = istr.at (i);    }}

This will be no problem.

What if we must use the string type? This can be done by using string to preserve the principle of characters

void foo (conststring& iStr) {    string  str;      for (int0; i < istr.length (); + +i)        {= istr.at (i);    }}

Separating the object instance from the assignment does not occur.

[017]string Class Usage precautions