Hello. In an example of one library, I met the following code:
const char* ssid = "My_WiFi_ssid";
const char* password = "My_WiFi_password";
And then running
WiFi.begin(ssid, password);
Why? for What?
If I understand correctly, then two pointers are created, and addresses are written in them as a string? And then this "address" is read, which is a "string".
Why not create a simple string and access the contents of that variable?
What do you consider a "simple string"?
You are passing these two pointers to WiFi.begin which sets up some conditions necessary.
In WiFi.begin the pointers are used to retrieve the string data.
String ssid = "My_WiFi_ssid";
or
char ssid[32] = "My_WiFi_ssid";
Well this is a waste of about 25 bytes:
char ssid[32] = "My_WiFi_ssid";
You could use
const char ssid[] = "My_WiFi_ssid";
Why are we writing the string where the address should be?
Whatever that means...
The pointers (each 2 bytes each) are passed, not the strings.
These pointers say where to find the strings.
Why is it used
const char* ssid = "My_WiFi_ssid";
not this?
const char myssid[] = "My_WiFi_ssid";
const char *ssid = myssid[];
But nobody created the string themselves. Or are they created at the moment of declaring a pointer with a value?
have a read about const pointers and pointers to const values
My personal preference is the following, which creates the char arrays and stores the text in them.
const char ssid[] = "My_WiFi_ssid";
const char password[] = "My_WiFi_password";The original version, without any compiler optimizations, would store the text in char arrays, then create a separate char* to store the pointer to the char array, using more memory in the process. As a practical matter, the compiler likely never actually stores the pointers.
const char* ssid = "My_WiFi_ssid";
const char* password = "My_WiFi_password";This will likely not compile, and basically does the same as the original, except that myssid can now be referenced in the code separately from ssid.
< edit > The most common reason for doing it this way, creating the char array and char* separately, is when you want the compiler to store both in the flash memory on a processor that has flash memory in a separate address space from the ram (reference the use of PROGMEM).
const char myssid[] = "My_WiFi_ssid";
const char *ssid = myssid[]; //likely compiler error because of the []Thanks! This is what I didn't understand.
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