What's wrong with my custom string class operator+? - c++

Question

I'm trying to make my own String class, and I have a problem with operator+.
When I use + as " s1 = s2 + s3 " it works.
But in case just use " s1 + s1 " or " s2 + s3 " does not work.
When I run it, I get 0xC0000005 error on 'init' function at delete[] str_; line.
I want to know what's wrong with my codes...
this is my string.h
class String
{
private:
int len_;
int capa_;
char* str_;
public:
String(const String& str);
String(const char* s = "");
~String();
const char* Print(bool show = true);
int size();
int length();
int capacity();
String& assign(const String& str);
String& assign(const char* s);
String& operator=(const String& str);
String& operator=(const char* s);
String& append(const String& str);
String& append(const char* s);
String& operator+=(const String& str);
String& operator+=(const char* s);
String operator+(const String& str);
String operator+(const char* s);
char& operator[](int index);
void shrink_to_fit();
friend std::ostream& operator<<(std::ostream& os, const String& str);
private:
void init(const char* s);
String plus(const char* s);
};
this is my string.cpp
void String::init(const char* s)
{
if (str_ == s) {}
else
{
delete[] str_;
}
len_ = strlen(s);
capa_ = len_ + 1;
str_ = new char[capa_];
strcpy_s(str_, capa_, s);
}
String::String(const String& str)
{
init(str.str_);
}
String::String(const char* s)
{
init(s);
}
String::~String()
{
delete[] str_;
}
int String::size()
{
return this->len_;
}
int String::length()
{
return strlen(this->str_);
}
int String::capacity()
{
return this->capa_;
}
String& String::assign(const String& str)
{
assign(str.str_);
return *this;
}
String& String::assign(const char* s)
{
init(s);
return *this;
}
String& String::operator=(const String& str)
{
assign(str.str_);
return *this;
}
String& String::operator=(const char* s)
{
assign(s);
return *this;
}
String& String::append(const String& str)
{
append(str.str_);
return *this;
}
String& String::append(const char* s)
{
len_ = this->len_ + strlen(s);
capa_ = len_ + 1;
char* temp = new char[capa_];
strcpy_s(temp, capa_, this->str_);
if (str_ == s) {}
else
{
delete[] str_;
}
strcat_s(temp, capa_, s);
str_ = new char[capa_];
strcpy_s(str_, capa_, temp);
delete[] temp;
return *this;
}
String& String::operator+=(const String& str)
{
append(str);
return *this;
}
String& String::operator+=(const char* s)
{
append(s);
return *this;
}
char& String::operator[](int index)
{
int index_;
if (index < 0)
{
index_ = 0;
}
else if (index > this->len_)
{
index_ = this->len_ - 1;
}
else
{
index_ = index;
}
return str_[index_];
}
String String::plus(const char* s)
{
int tempcapa = this->len_ + strlen(s) + 1;
char* temp = new char[tempcapa];
strcpy_s(temp, tempcapa, this->str_);
strcat_s(temp, tempcapa, s);
return temp;
}
String String::operator+(const String& str)
{
return plus(str.str_);
}
String String::operator+(const char* s)
{
return plus(s);
}
std::ostream& operator<<(std::ostream& os, const String& str)
{
os << str.str_;
return os;
}
void String::shrink_to_fit()
{
if (this->capa_ > this->len_ + 1)
{
char* temp = new char[len_ + 1];
strcpy_s(temp, len_ + 1, this->str_);
delete[] this->str_;
this->str_ = new char[len_ + 1];
strcpy_s(this->str_, len_ + 1, temp);
delete[] temp;
this->capa_ = len_ + 1;
}
}
const char* String::Print(bool show)
{
if (show == true)
std::cout << str_;
return str_;
}