Trying to properly substring with String - c++

Question

Given the following function:
If I execute setColor("R:0,G:0,B:255,");
I'm expecting the red, grn, blu values to be:
0 0 255 except I'm getting 0 0 0
It's working fine for R:255,G:0,B:0, or R:0,G:255,B:0, though.
int setColor(String command) {
//Parse the incoming command string
//Example command R:123,G:100,B:50,
//RGB values should be between 0 to 255
int red = getColorValue(command, "R:", "G");
int grn = getColorValue(command, "G:", "B");
int blu = getColorValue(command, "B:", ",");
// Set the color of the entire Neopixel ring.
uint16_t i;
for (i = 0; i < strip.numPixels(); i++) {
strip.setPixelColor(i, strip.Color(red, grn, blu));
}
strip.show();
return 1;
}
int getColorValue(String command, String first, String second) {
int rgbValue;
String val = command.substring(command.indexOf(first)+2, command.indexOf(second));
val.trim();
rgbValue = val.toInt();
return rgbValue;
}

Answer 1

Without knowing your String implementation, I can only make an educated guess.
What happens is that indexOf(second) doesn't give you what you think.
"R:0,G:0,B:255,"
^ ^- indexOf("B:")
|- indexOf(",")
It works for your other cases as none of the things they look for occur more than once in the string.
Looking at the SparkCore Docs we find the documentation for both indexOf and substring.
indexOf()
Locates a character or String within another String. By default, searches from the beginning of the String, but can also start from a given index, allowing for the locating of all instances of the character or String.
string.indexOf(val)
string.indexOf(val, from)
substring()
string.substring(from)
string.substring(from, to)
So now to fix your problem you can use the second variant of indexOf and pass that the index you found from your first search.
int getColorValue(String command, String first, String second) {
int rgbValue;
int beg = command.indexOf(first)+2;
int end = command.indexOf(second, beg);
String val = command.substring(beg, end);
val.trim();
rgbValue = val.toInt();
return rgbValue;
}

Answer 2

In this instance, I would split the string using a comma as the delimiter then parse each substring into a key-value pair. You could use a vector of value for the second part if you always have the sequence "R,G,B" in which case why have the "R:", "G:" or "B:" at all?

Answer 3

I can suppose that command.indexOf(second) will always find you the first comma, therefore for B the val becomes empty string.
Assuming that indexOf is something similar to .Net's, maybe try
int start = command.indexOf(first)+2;
int end = command.indexOf(second, start)
String val = command.substring(start+2, end);
Note the second argument for the second call to indexOf, I think it will make indexOf to look for matches after start. I also think you'd better pass a "," as a second for all calls, and add +1 or -1 to end to compensate for this passing "," instead of "G" and "B".
Or just use another limiter for B part, like R:0,G:0,B:0. (dot instead of comma).

Answer 4

I ended up just modifying my code:
int setColor(String command) {
int commaIndex = command.indexOf(',');
int secondCommaIndex = command.indexOf(',', commaIndex+1);
int lastCommaIndex = command.lastIndexOf(',');
String red = command.substring(0, commaIndex);
String grn = command.substring(commaIndex+1, secondCommaIndex);
String blu = command.substring(lastCommaIndex+1);
// Set the color of the entire Neopixel ring.
uint16_t i;
for (i = 0; i < strip.numPixels(); i++) {
strip.setPixelColor(i, strip.Color(red.toInt(), grn.toInt(), blu.toInt()));
}
strip.show();
return 1;
}
I simply just do: 255,0,0 and it works a treat.