Learn how to fix error: no instance of overloaded function matches the argument list.

Question

I encountered the following problem in completing my work:

No instance of overloaded function matches argument list

Below is the code I ran:

#define _CRT_SECURE_NO_WARNINGS
 #include <iostream>
 #include <string>
 
 using namespace std;
 
 class String
 {
 private:
 char str[100]; 
 char cpy[100];
 public:
 
 static const char NULLCHAR = '\0';
 
 String()
 {
  str[0] = NULLCHAR;
  cpy[0] = NULLCHAR;
 }
 
 String(char* orig, char* cpy)
 {
  Copy(orig, cpy);
 }
 
 void Display()
 {
  cout << str << endl;
 }
 
 void Copy(char* orig, char* dest)
 {
 
  while (*orig != '\0') {
  *dest++ = *orig++;
  }
  *dest = '\0';
 
 
 
 }
 
 void Copy(String& orig, String& dest) 
 {
  Copy(orig.str, dest.cpy);
 }
 
 void Concat(char* orig, char* cpy)
 {
  while (*orig)
  orig++;
 
  while (*cpy)
  {
  *orig = *cpy;
  cpy++;
  orig++;
  }
  *orig = '\0';
 
 }
 
 void Concat(String& orig, String& cpy)
 {
  Concat(orig.str, cpy.cpy);
 }
 
 int Length(char* orig)
 {
  int c = 0;
  while (*orig != '\0')
  {
  c++;
  *orig++;
  }
  printf("Length of string is=%d
", c);
  return(c);
 
 }
 };
 
 int main()
 {
 String s;
 
 s.Copy("Hello");
 s.Display();
 s.Concat(" there");
 s.Display();
 
 String s1 = "Howdy";
 String s2 = " there";
 String s3;
 String s4("This String built by constructor");
 s3.Copy(s1);
 s3.Display();
 s3.Concat(s2);
 s3.Display();
 s4.Display();
 
 
 system("pause");
 return 0;
 }

What's causing it, and how can it be resolved in the “no instance of overloaded function matches the argument list“ in the cpp?

lyytutoria · Accepted Answer

The cause:

Although you a constructor that has two parameters and a default one, there is not a constructor for your String type that just accepts one argument. Therefore, the error happens.

Solution:

To solve this problem, you need to specify a constructor which accepts an unique parameter and initializes the string.

Another way is copying your Copy and Concat functions which you give an unique parameter into a String object as the following:

String Copy(char* orig)
{
// The identical copy logic you possess,
// don't copy into "*here"
}

Léo Grandjean · Answer

Your Copy and Concat function take two parameters. However, you only pass one parameter to them. Your code should look something like this if you want to copy them into String objects.

String Copy(char* orig)
{
 // Same copy logic you have, 
 // except copy into "*this"
}

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Learn how to fix error: no instance of overloaded function matches the argument list.