Time for action - making the calculator buttons

Using the screenshot shown at the start of this chapter as a guide, let's build the calculator buttons (the scripts you will type are also listed if you later want to make sure you typed them correctly):

1. If you're not already there, go to the second card, the currently empty one.
2. Make sure the Edit button is selected in the Tools palette and drag a Push button to the card, to the position of the 7 button.
3. In the Basic Properties panel of the Inspector palette, set the Style drop-down menu to Rounded Rectangle (in real life, you would take the time to have nice graphical buttons; here, you are just matching my ugly "programmer art"!).
4. Set the name of the button to number7 and the label to 7.
5. Select Object Script from the Object menu to see the starter script as you did with the Begin button.
6. In the empty line between on mouseUp and end mouseUp, type numberPressed the label of me. Note that numberPressed is a new handler that needs to be defined later. When used, me refers to the current object; in this case, the button pressed.
7. Close and save the script.
8. Select the button and make a copy of it by choosing Duplicate Objects from the Edit menu and position it where the 8 button will be. Copy/Paste and Alt-drag are two other ways to duplicate an object.
9. Set the name to number8, and label to 8.
10. Repeat steps 8 and 9 for the buttons 9, 4, 5, 6, 1, 2, 3, 0, and the decimal point using the corresponding number instead of 8. For the decimal point, let the name be decimalpoint.
11. Duplicate one of the buttons again, name the new button divide, and type / for its label.
12. Select Object Script for the divide button and change numberPressed in the middle line to say operatorPressed, making the whole line operatorPressed the short name of me.
13. Duplicate the divide button three more times and set the names to multiply, plus, and minus. Set the labels to *, +, and -.
14. Duplicate the divide button again, giving the new button a name equals and a label =, and change the middle line of script to say equalsPressed.
15. Duplicate the = button and set the new button's name to toggleSign and label to +-; then, change the middle line of script to toggleSign.
16. Duplicate the = button and set the new button's name to clear and label to C; then, change the middle line of script to be clearPressed.
17. Drag a Label field from the Tools palette and in the Inspector palette, choose Text Formatting from the drop-down menu. In the Text Formatting settings, choose a nice looking font, right-justified text, and a large font size. Name the field display.
18. Edit the script of the display field. With fields, you don't get the starter script that you get with buttons, so you will need to type the mouseUp lines yourself. Type these three lines in the script: on mouseUp, set the clipboarddata["TEXT"] to me, and end mouseUp. DO enter the quote marks on either side of the word "TEXT".
19. Move all the buttons in their right spots and select the sets of buttons to then use the Align tools and make your calculator layout match the screenshot.
20. Save it now!

What just happened?

Quite a lot just happened! We have now made all the card level objects and typed in their scripts. Most of the scripts are "calling" up to a card level handler that we will be setting up next. Before doing that, it's worth trying to understand some of the lines we just entered.

Verbosity, synonyms, and "me"

The English-like nature of the programming language in LiveCode is amazingly powerful, but rigidly so. In some other tools, you have a choice of whether you want to use verbose English-like syntax, less verbose, or what is called dot syntax. The Lingo language, in Adobe Director, is a good comparison.

Suppose we want to change the text inside a field, that is the first entry of a director movie's cast, we can perform the following verbose syntax:

We can perform a slightly less verbose syntax:

Or, we can perform a dot-syntax:

In LiveCode, there isn't a choice. What you type has to be in the form of:

However, you do have a choice about whether to use a long version of a word, short version, or an abbreviated form. There are also synonyms, which allow you to use a word that makes more sense to you.

Here are the two ways of saying the same thing, with the second variation using an abbreviated form of the keywords:

When you are dealing with the contents of the object that has the script running, you can use the keyword me to save on some typing, and LiveCode will also try to work out what you have in mind, if possible.

Take the lines we have entered as examples:

Here, numberPressed will propagate up to a card handler that we will add (soon) and the label of me will look at the Label that you have set for the object that the script is inside of:

In this case, me would normally refer to the object (as is the case with the label of me), but because we gave the extra clue of ["TEXT"], LiveCode knows that it's the text contents of the field that have the script and not the field itself. Still, because there is potential for confusion, when reading your own code later, you could add a couple of words to make the meaning more clear:

Note

By the way, the display field script is not needed for the calculator to work. It's just there so that at any point of time, you can click on the field and have the current value copied to the clipboard in order to paste it in other applications.

You might choose to be more verbose than is needed, just for readability reasons, and in these chapters, this is going to be the case. It is easier to tell what is going to happen by using:

The following will be less verbose compared to the preceding entry, even though they are equally valid:

In either case, as it's a field, LiveCode knows what you meant.

You see in the script that we typed short name of me, what's that all about? Objects in LiveCode have a lengthy description of where they are located, for example, the buttonname button of the 1234 card ID of the path/to/stack.livecode stack. In the calculator application, we need only the single word that you set as the name of the button. If we asked for name of me, it would still say "the buttonname button". To just grab the name itself, we use short name of me.

There are times when you will want to use the other variations of name, including the long name and the abbreviated name, which you can read about in the LiveCode Dictionary entry for name. In addition to a description of the different ways to use name, there are a number of cautions you need to be aware of.

Tip

Case sensitivity

If any of you use advanced LiveCode, you may notice that in some cases, I have the casing wrong. LiveCode doesn't mind what casing you have used and so, when I incorrectly said clipboarddata instead of clipboardData, it didn't matter. This feature isn't unique to LiveCode, but it is common among near-English programming languages to not demand that the user gets the casing exactly right before the command works.

Adding the card handlers

If you dared to go ahead and tried using the calculator buttons, you will see a lot of script errors. We need to add in the card level handlers to be at the receiving end of the calls that the buttons make. Instead of walking you through, typing a line of code at a time, it probably would be quicker to present the lines in one go and explain what each...