Hello I have an Arduino programme that has a string with the words hello in it. I can add characters and other strings to the end of that one using:
String test = "hello";
test+=" jack";
it would then say "hello jack" The problem is I want to get rid of the last character of the string every 2 seconds so it would be "hello jac" then "hello ja" and so on. How can I do this?
You may use remove() method to remove last character.
String s = "1234567890";
while(s.length() > 0) {
int lastIndex = s.length() - 1;
s.remove(lastIndex);
Serial.println(s);
}
Sstring and lenght.
I want to get rid of the last character of the string every 2 seconds so it would be "hello jac" then "hello ja" and so on. How can I do this?
This is how you could do that. Avoid using String and putting the string constants in program memory.
// A buffer for the message
const size_t MSG_MAX = 16;
char msg[MSG_MAX];
void setup()
{
Serial.begin(9600);
while (!Serial);
}
void loop()
{
static int len = 0;
// Check if it is time to create the initial message
if (len == 0) {
strcpy_P(msg, (const char*) F("hello"));
strcat_P(msg, (const char*) F(" jack"));
len = strlen(msg) - 1;
}
// Otherwise shorten the message
else {
msg[len--] = 0;
}
// And print current message
Serial.println(msg);
delay(2000);
}
You are best of learning about C-style strings rather than the String class. The String class can eventually fragment dynamic memory.
To shorten a string a simple method is to move the "string terminator" inwards by overwriting the last byte of the message with zero, like this:
const size_t MSG_MAX = 20;
char msg [MSG_MAX];
void setup ()
{
Serial.begin (115200);
Serial.println ();
strcpy (msg, "hello"); // initial message
strcat (msg, " jack"); // concatenate more stuff
} // end of setup
void loop ()
{
if (strlen (msg) > 0)
{
Serial.println (msg); // display current message
msg [strlen (msg) - 1] = 0; // move null-terminator in
delay (1000);
} // end of any message left
} // end of loop
Results:
hello jack
hello jac
hello ja
hello j
hello
hello
hell
hel
he
h