Concatenated String Doesn't Send Correctly
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Hi all!
I'm working with sending messages from one of my sensors back to my controller for the first time, and I'm a little stumped...
I have this message defined:
MyMessage msg(CHILD_ID_LIGHT, V_VAR1);
And this code that uses it to send a message to the controller
void open_scratchpad(int expectedScratchpadValues) { send(msg.set("Scratchpad is open")); send(msg.set("string " + String(expectedScratchpadValues))); }
I expect to get the following messages back (in this example, expectedScratchpadValues=4):
2;1;1;0;24;Scratchpad is open 2;1;1;0;24;string 4
Instead, I get:
2;1;1;0;24;Scratchpad is open 2;1;1;0;24;0
But if I do
Serial.println("string " + String(expectedScratchpadValues)
then the arduino console correctly prints
string 4
Never mind the exact code here. I'm just playing around to learn the messaging protocol, so it really doesn't mean much of anything. I just want to be able to convert ints to strings, concatenate those strings, and then pass that concatenated result back to my controller.
Thanks for you help!
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@mrmuszynski
Hi, there are some setters for message payload types but none for type String, see: Message manipulation.You need to convert the resulting String into const char* like this:
send(msg.set(("string " + String(expectedScratchpadValues)).c_str()));
But in general I would try to avoid usage of the String data type, especially for the use case in your code example. You could use e.g.:
char str[80]; sprintf(str, "string %d", expectedScratchpadValues); send(msg.set(str));
For Arduino String read more e.g. here: The Evils of Arduino Strings
HTH
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