Is there any way to separate this short code into its own function? (webserver, trying to use client.print outside of main loop)

Question 1

I have an arduino webserver that uses the following code:

client.println(F("HTTP/1.1 200 OK"));
client.println(F("Content-Type: text/html"));
client.println();
client.println(F("<HTML><HEAD>"));
...
if (fan1Toggle == 0)
 client.print(F("Fan1<font color=\"red\">&#8226;</font><a href=\"/?fan1on\">On</a><br>"));
else
 client.print(F("Fan1<font color=\"green\">&#8226;</font><a href=\"/?fan1off\">Off</a><br>"));
if (fan2Toggle == 0)
 client.print(F("Fan2<font color=\"red\">&#8226;</font><a href=\"/?fan2on\">On</a><br>"));
else
 client.print(F("Fan2<font color=\"green\">&#8226;</font><a href=\"/?fan2off\">Off</a><br>"));
...

The page is pretty long, allowing the user to toggle over a dozen different switches. Some of the code checks to see the state of a certain switch, and then displays a green or red bullet ("&#8226", like •) on the page if the switch is on or off.

Since the code for the colored bullet is repeating, I wanted to make a function for it. Then I would just call (for example) "displayBullet(fan1Toggle);", and it would determine if fan1 was on or off, and display the correct color depending on the state.

I tried to create the following function:

void displayBullet(int toggle) {
if (toggle == 0) //switch is off, so display red bullet
 client.print(F("<font color=\"red\">&#8226;</font>"));
else //switch is on, so display green bullet
 client.print(F("<font color=\"green\">&#8226;</font>"));
}

But then I got an error saying that "'client' is not declared in this scope".

Is there any way to work around that error, so that I can get the displayBullet() function I want? Or is this something that can't be shortened like this, because the "client" function has to be inside the main loop?

Thanks!

Question 2

You can pass client to the function by reference, like this:

void displayBullet(EthernetClient & client, int toggle) 
 {
 if (toggle == 0) //switch is off, so display red bullet
 client.print(F("<font color=\"red\">&#8226;</font>"));
 else //switch is on, so display green bullet
 client.print(F("<font color=\"green\">&#8226;</font>"));
 }

Now it knows about client. Make sure you pass client when you call it:

displayBullet(client, 1);

Question 3

Thanks a lot!! That's very useful information to know, and I'm sure it'll help me in the future with other similar problems.

Nick Gammon ♦Nick Gammon 38.9k13 gold badges69 silver badges125 bronze badges · Accepted Answer · 2015-08-05 21:52:27Z

You can pass client to the function by reference, like this:

void displayBullet(EthernetClient & client, int toggle) 
 {
 if (toggle == 0) //switch is off, so display red bullet
 client.print(F("<font color=\"red\">&#8226;</font>"));
 else //switch is on, so display green bullet
 client.print(F("<font color=\"green\">&#8226;</font>"));
 }

Now it knows about client. Make sure you pass client when you call it:

displayBullet(client, 1);

Thanks a lot!! That's very useful information to know, and I'm sure it'll help me in the future with other similar problems.

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Is there any way to separate this short code into its own function? (webserver, trying to use client.print outside of main loop)

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