different methods to compare strings not working

Projects Programming
1

Aloha folks,

I am attempting to compare characters gathered from a keypad to a code "123" While searching the forums, I came upon a couple solutions:

I've tried using "strcmp (strcmp(key, "123") == 0" //I've also tried setting a string variable to 123 and using the string instead of "123"
I get this error:

Keypad_Screen_ino.ino: In function 'void loop()':
Keypad_Screen_ino:49: error: cannot convert 'String' to 'const char*' for argument '1' to 'int strcmp(const char*, const char*)'

I've also tried "if (key.contains("123"))" and received this error:

Keypad_Screen_ino.ino: In function 'void loop()':
Keypad_Screen_ino:50: error: 'class String' has no member named 'contains'

I've included my overall code below:

#include <Keypad.h>
#include "U8glib.h"
#include <WString.h>

U8GLIB_ST7920_128X64 u8g(13, 11, 12, U8G_PIN_NONE);

const byte ROWS = 4; 
const byte COLS = 4; 
char keys[ROWS][COLS] = {
  {'1','2','3','<'},
  {'4','5','6','>'},
  {'7','8','9','='},
  {'*','0','I','U'}
};
byte rowPins[ROWS] = {2,3,4,5}; //connect to row pinouts 
byte colPins[COLS] = {6,7,8,9}; //connect to column pinouts

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

String key;  // key should be a global variable, written in "loop()" and read in "draw()"
char tempkey;

void draw(void) {
  u8g.setFont(u8g_font_osb18);
  u8g.setPrintPos(0, 18);
  u8g.print(key); 
}

void draw2(void) {
  u8g.setFont(u8g_font_osb18);
  u8g.setPrintPos(0, 60);
  u8g.print(key); 
}

void setup(){
  Serial.begin(9600);
}
void loop(){
  String solution = "123";
  tempkey = keypad.getKey();
  if (tempkey != NO_KEY){
    key = key+tempkey;
    Serial.println(key);
    u8g.firstPage();
    do {
      draw();
    } while( u8g.nextPage() );
    //if (strcmp(key, "123") == 0){
    //if (strcmp( key, solution ) == 0 ){
      if (key.contains("123")) {
      do {
        draw2();
      } while( u8g.nextPage() );
    }
 }
}

Any ideas would be most appreciated!

2

strcmp works on character arrays. String is an object and you should use the function equals() (see: equals() - Arduino Reference)

example:

    if (key.equals("123") ){
        //
        // equals returns true if equal
        //
3 
if (key == "123") 
 ...
4

Both of thoes work, thanks!

I could have SWORN the first thing I tried was if (key == "123"){

Ah well, thanks : )