The send command vs the call command

[nlexa]

Make a new stack
Make 2 cards

On card 1 create a text field and name it "theField"
In field "theField" script write the custom command:

on thisCommand
put "Blue" into field "theField"
end thisCommand


On card 2 create a button
on mouseUp
send "thisCommand" to field "theField" of card 1
end mouseUp

Press the button on card 2 and see if it works;
You should get this error:
field "theField": execution error at line 2 (Chunk: no such object) near "theField", char 15

if however you change 'thisCommand' to say:

on thisCommand
put "Blue" into field "theField" of card 1
end thisCommand

Then it works and puts the word "Blue" into the field.
I don't understand how the command cannot find the field in the first example and causes the error.

If I were to call this command from card 1 from a similar button it would work.
Make a button on card 1 and in the script write:

on mouseUp
send "thisCommand" to field "theField"
end mouseUp

Does this mean every object I reference in a custom command that I intend to use with the 'send' command from another card need to be explicitly declared ( of card 1 ).
I assume the answer is yes.

After having just read the manual section entitled "The send Command versus the call Command" I find this behaviour peculiar and contrary to the manual.
Can someone correct me?

[BarrySumpter]

yes, very interesting question and behaviours.
Thats an intricate question for your first post.
Welcome to the forums.

I'd prefer you upload a complete .livecode project to make it easier and to ensure we're testing the same project.

I thnk error is expecting field "theField" to be on card 2 and can't find it.

But I've drawn the same logical conclusion from your post without actually testing it myself.

5.8.6 The send Command versus the call Command
The call command is similar to the send command. Like the send command, the
call command sends a message to the specified object, allowing you to use handlers
that aren't in the message path.
The difference between send and call is how they handle object references in the
handler that is triggered by the sent message. If the message is sent by the send
command, object references in the handler are treated relative to the object you sent the
message to.

For example, suppose card 1 of a stack contains the following handler:

Code: Select all

on showCard
answer the number of this card
end showCard

If a handler in the script of card 3 uses the send command to send a "showCard"
message to card 1, the dialog box displays "1", the number of the card the handler is on.
However, if the same handler uses the call command instead, the dialog box displays
"3", the number of the card that used the call command. In other words, handlers that
are triggered by the send command use the context of the object the handler is in, while
handlers that are triggered by the call command use the context of the object that
triggered the handler.

[nlexa]

I would love to upload the .livecode file but the file extension is not allowed. neither is .txt and I can't trick it with .jpg

The difference between send and call is how they handle object references in the
handler that is triggered by the sent message. If the message is sent by the send
command, object references in the handler are treated relative to the object you sent the
message to.

As far as I can tell, this is rubbish. This is frustrating. I'm trying to learn livecode and when I write myself an example to test, it doesn't behave anything like the manual entry.

[SparkOut]

Try zipping the file first, it should be accepted for upload then.

[BarrySumpter]

There are some restrictions for new forum members.

Hyperlinks were allowed only after 10 posts or 7 days.
To keep spammers away.

Don't know the rules for attachments.

[nlexa]

Sendcommandproblem.zip

(903 Bytes) Downloaded 288 times

thanks guys. I will be interested to see what I did wrong.

[Klaus]

Hi nlexa,

you did nothing wrong and this is correct behavior!

This is not easy to explain...

The "world" of LiveCode consists of the current card only, so when you "send" you handler to a button on another card,
that handler will also only "see" the current card and does not find that namely field!
But it DOES if we are (the LiveCode "world" is) on the card with the button!

So you should simply add a descriptor of that card (number or name) and everything will be fine:

Code: Select all

on thisCommand
  put "Blue" into field "theField" OF CD "name of card here"
end thisCommand

Just like you did in your "send" handler!
...
send "thisCommand" to field "theField" of card 1
...


Best

Klaus

[nlexa]

Thanks Klaus! I thought that might be the case because I tried using:

on mouseUp
go to card 1
send thisCommand to field "theField" of card 1
end mouseUp

this works because it goes to the card before it sends the message to it.
In any case I had to hear it from someone else to be sure that:

The "world" of LiveCode consists of the current card only

[Klaus]

Yep, it's a small world, but the best (and only) we have