Preference fetchString not working..... user error?

[chrisvandiemen]

I've got some issues with the Preferences library for Arduino.

The following snippet is responsible for storing a variable to EEPROM:

Code: Select all

int DeviceSettings::storeString(const char* key, const char* value){
  preferences.begin(name_space, false);
  Serial.println(preferences.putString(key, value), DEC);
  preferences.end();
}

This outputs '16', which is correct given the input I give it.

When i try to fetch the before stored variable using this code:

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void DeviceSettings::fetchString(const char* key, char* value){
  preferences.begin(name_space, false);
  Serial.println(preferences.getString(key, value, 200), DEC);
  Serial.println(value);
  preferences.end();
}

This outputs '0' and ''

I can't seem to understand what's happening. Both methods receive the same key:

Code: Select all

 settings.storeString(SETTINGS_APP_NAME,"Chris van Diemen");
  char * s;
  settings.fetchString(SETTINGS_APP_NAME, s);

Is this user error of is there something else going on?

[tele_player]

At the very least, your final snippet doesn't allocate any space for
char * s;

So, s is a pointer which doesn't point to any storage.

[martinayotte]

You should not using "char *s;" to define your variable, since it is an unallocated pointer, but use "char s[200];" instead ...