CODEWITHSUNDEEP
c++stringstructchartypedef
Plàcid Masvidal
Plàcid Masvidal

Reputation: 140

Why can't I initialize a typedef struct string or char as normally?

I'm begginer in programming and C++.

Programming on Linux, I am creating a typedef struct as below:

typedef struct {

    char id[10];
    string name[20];    

}Employee;

Usually, when not using struct, I initialize string char doing: 

char id[10]="ID02093";
string name="Joe";

So, why can't I initialize char id and string name of the Employee struct as below?:

Employee salesManager;
salesManager.id="ID02093";
salesManager.name="Joe";

I'm getting this errors from the g++ compiler:

"incompatible types in assignment of ‘const char [8]’ to ‘char [9]’ salesManager.id="ID02093";" incompatible types in assignment of ‘const char [4]’ to ‘std::__cxx11::string [20] {aka std::__cxx11::basic_string [20]}’ salesManager.name="Joe";

What's the right way to initialize string and char of typedef struct elements out of the typedef struct declaration?

Upvotes: 0

Views: 2116

Answers (3)

jxh
jxh

Reputation: 70392

You cannot assign to an array of char

Considering this line:

salesManager.id="ID02093";

You are allowed to initialize an array of char with a string literal as a convenience allowed by the syntax C++ inherited from C. However, you are not permitted to use assignment with an array. Which is why you got this error:

incompatible types in assignment of ‘const char [8]’ to ‘char [9]’ salesManager.id="ID02093";

Instead, you have to copy the data into the array.

You cannot assign to an array of string

Considering this line

salesManager.name="Joe";

The reason this failed is because you had declared name to be an array as well.

typedef struct {

    char id[10];
    string name[20];    

}Employee;

This explains why you got this error:

incompatible types in assignment of ‘const char [4]’ to ‘std::__cxx11::string [20] {aka std::__cxx11::basic_string [20]}’ salesManager.name="Joe";

You likely did not mean to declare name to be an array.

Avoid using anonymous classes

A typedef name given to an anonymous class type has slightly different semantics from a class name. Since the differences are tricky, it is best to avoid using anonymous classes if it is not contained within a class itself.

Upvotes: 0

Keith Thompson
Keith Thompson

Reputation: 263217

Initialization and assignment are two distinct (but similar) things.

You can initialize an array by providing a value for it when you declare/define it.

You cannot assign to an array.

You can copy a value into an array using memcpy or strcpy:

char name[20];
strcpy(name, "Test";

But for your purposes, you can initialize the array as part of the initialization of the structure:

typedef struct {
    char id[10];          
    char name[20];
} Employee;
Employee salesManager = {
    "A12345678",
    "Test"
};
/* OR */
Employee salesManager = {
    .id = "A12345678",
    .name = "Test"
};

Since you're asking about C++ rather than C, it's probably better to use std::string rather than raw character arrays. std::string is a lot more flexible: you can assign values, including string literals, to std::string objects.

Upvotes: 4

Esdras Xavier
Esdras Xavier

Reputation: 863

I think you should use string in both cases, and use OOP instead of typedef. But try this code bellow, should work fine:

#include <iostream>

using namespace std;

typedef struct {

    string id;
    string name;    

} Employee;


int main() {
    Employee salesManager;
    salesManager.id = "A12345678";
    salesManager.name = "Test";

    cout << "Id: " << salesManager.id << endl;
    cout << "Name: " << salesManager.name << endl;

    return 0;
}

Upvotes: 0

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