TweetFollow Us on Twitter

Thinking Logically

Volume Number: 21 (2005)
Issue Number: 1
Column Tag: Programming

AppleScript Essentials

by Benjamin S. Waldie

Thinking Logically

Last month, we explored adding different types of repeat loops to scripts, which is a very important and useful aspect of AppleScript development. As we discussed, by allowing you to perform a series of repetitive tasks without the need to duplicate code, repeat loops help to make your code less verbose, more efficient, and easier to change in the future. This month, we will focus on adding logic to your scripts, which is another important part of AppleScript development.

In AppleScript, a script can be written to logically determine a specific course of action, based on criteria that you define. For example, a backup script might be written to perform a specific backup process, based on the user that triggers the script, or based on the day of the week. While this is a fairly simple example, the point is, by adding logic to a script, the script can actually make decisions about which tasks should be performed.

If/Then Statements

Adding logic to a script is done with the addition of an if/then statement. If/then statements can range from the simple to the extremely complex.

When you write a script, you write a series of instructions for AppleScript to perform when the script is run. Each of these instructions is considered to be a statement. Simple statements are written as single lines of code. Compound statements are AppleScript statements that are written as more than one line of code. Compound statements contain other AppleScript statements, and always end with an end clause. Tell statements, repeat statements, and if/then statements would be considered compound statements.

Basic If/Then Statements

The most basic form of the if/then statement appears as follows:

if boolean expression then 
 do something 
end if

You can see from the example above, that a boolean expression is used as the basis for the if/then statement. In if/then statements, a boolean expression must evaluate to a value of true in order for the desired code, specified above as do something, to be executed.

In AppleScript, an expression is defined as a series of terms that evaluates to a value. For example, the following code would be considered an expression in AppleScript, and evaluates to a value of 2: 1 + 1 A boolean expression is considered to be any expression that evaluates to a true or false value.

Below is a functional example of a basic if/then statement:

set theOutputFolderPath to path to desktop folder 
set theNewFolderName to "My Folder"

tell application "Finder"

 if (exists folder (theOutputFolderPath & theNewFolderName as string)) = false then 
  make new folder at desktop with properties {name:theNewFolderName} 
 end if 
end tell

In the example above, the first two lines set up variables containing an output folder path and a folder name. Next, the if/then statement determines whether the folder already exists, and it triggers code to create the folder if it does not already exist.

As I said above, a boolean expression in an if/then statement must evaluate to a true value. To fully understand this, let's look at the boolean expression from our example in a little more detail. The complete boolean expression to be evaluated is the following:

(exists folder (theOutputFolderPath & theNewFolderName as string)) = false

We can break down this boolean expression into two separate parts. In the first part, the Finder's exists command is used in order to determine whether the folder already exists, and is represented by the following code:

(exists folder (theOutputFolderPath & theNewFolderName as string))

The second part of the boolean expression determines whether the result of the first part is equal to a value of false, and is represented by the following code:

= false

Looking at both parts of the boolean expression together again as a whole, if the result of the exists command is equal to false, then the second part of the boolean expression confirms that the first part is equal to false. Therefore, the boolean expression as a whole has been determined to be true, and the next part of the code will be executed, thus creating the folder.

Initiating a Second Course of Action

It is also possible to initiate a second course of action, should the boolean expression evaluate to a value of false. This is done through the addition of an else clause to the if/then statement. For example:


if boolean expression then 
 do something 1 
else 
 do something 2 
end if

Let's add an else clause to our example from above that creates a folder. In the following example, if the folder does not already exist, then it will be created. However, if the folder does already exist, then the user will be presented with a dialog indicating that a new folder was not created because one already exists.

set theOutputFolderPath to path to desktop folder 
set theNewFolderName to "My Folder"

tell application "Finder"

 if (exists folder (theOutputFolderPath & theNewFolderName as string)) = false then 
  make new folder at desktop with properties {name:theNewFolderName} 
 else 
  display dialog "Did not create a folder because one already exists."

 end if 
end tell

Even with the use of basic if/then statements, you can already begin to see that if/then statements can provide a lot of flexibility with regard to the behavior of a script.

Combining Boolean Expressions

In certain instances, you may need to combine more than one boolean expression together in order to create a new, more complex boolean expression. This can be done with the use of the and or the or AppleScript operator. For example:

boolean expression and boolean expression

boolean expression or boolean expression

In either of the above cases, the entire expression will evaluate to a true or false value. In the first instance, each boolean expression must evaluate to a value of true in order for the entire expression to evaluate to a value of true. In the second instance, if either of the boolean expressions evaluates to a value of true, then the entire expression will evaluate to a value of true.

The following example uses a combination of two boolean expressions in order to determine whether to create a folder called My Tuesday Folder. One boolean expression determines whether the folder already exists. The other determines if the current date is a Tuesday. In this example, each of these boolean expressions must evaluate to a value of true, making the entire expression evaluate to a value of true, in order for the folder to be created.

set theOutputFolderPath to path to desktop folder 
set theNewFolderName to "My Tuesday Folder"

tell application "Finder"

 if (exists folder (theOutputFolderPath & theNewFolderName as string)) = 
	false and (weekday of (current date)) = Tuesday then 
  make new folder at desktop with properties {name:theNewFolderName} 
 end if 
end tell

Complex If/Then Statements

As we have seen so far, the most basic form of the if/then statement evaluates a boolean expression in order to determine whether a specific course of action should occur. An if/then statement of this nature also allows you to take an alternate course of action, if desired. However, in some cases, you may need to evaluate a boolean expression against multiple criteria, taking multiple courses of action depending on the results. This can be done by extending the else clause in the if/then statement to an else if clause. For example:

if boolean expression then 
 do something 1 
else if boolean expression then 
 do something 2 
end if

In the following example, the user is prompted, with a displayed dialog, to click a button indicating whether a folder should be created. In the dialog, the user is presented with 3 buttons - Yes, No, and Maybe Later. With the use of a more complex if/then statement, the script performs a different action, based on the button clicked by the user. If the user clicks the Yes button, then the folder is created on the desktop. If the user clicks the No button, then the folder is not created. If the user clicks the Maybe Later button, then the user is prompted to trigger the script again when ready to create the folder.

set theButton to button returned of 
(display dialog "Would you like to create a new folder on the desktop?" 
buttons {"Yes", "No", "Maybe Later"}) 
set theOutputFolderPath to path to desktop folder 
set theNewFolderName to "My Folder"

if theButton = "Yes" then 
 tell application "Finder"

  make new folder at desktop with properties {name:theNewFolderName} 
 end tell 
else if theButton = "Maybe Later" then 
 display dialog "Trigger the script again when you are ready to build a folder."

end if

Optionally, you may still choose to include an else clause in this type of if/then statement, if desired. For example, we could add an else clause to our code above in order to display a notice to the user if the No button is clicked.

set theButton to button returned of 
(display dialog "Would you like to create a new folder on the desktop?" buttons 
{"Yes", "No", "Maybe Later"}) 
set theOutputFolderPath to path to desktop folder 
set theNewFolderName to "My Folder"

if theButton = "Yes" then 
 tell application "Finder"

  make new folder at desktop with properties {name:theNewFolderName} 
 end tell 
else if theButton = "Maybe Later" then 
 display dialog "Trigger the script again when you are ready to build a folder."

else 
 display dialog "A folder has not been created."

end if

Nested If/Then Statements

Another effective way to create complex if/then statements is through the nesting of if/then statements.

If you are not new to scripting, then you may be familiar with nesting already. Nesting refers to the placement of one type of AppleScript statement within another statement of the same type.

An example of a nested if/then statement's syntax would be the following:

if boolean expression then 
 if boolean expression then 
  do something 1 
 end if 
else if boolean expression then 
  do something 2 
end if

Looking back again to our folder creation example, the following code has been modified to include a nested if/then statement. Should the user choose to click the Yes button to create a new folder, a second if/then statement will be executed. This will determine whether the folder exists before creating it, taking a different course of action if it does already exist.

set theButton to button returned of (display dialog "Would you like 
to create a new folder on the desktop?" buttons {"Yes", "No", "Maybe Later"}) 
set theOutputFolderPath to path to desktop folder 
set theNewFolderName to "My Folder"

if theButton = "Yes" then 
 tell application "Finder"

  if (exists folder (theOutputFolderPath & theNewFolderName as string)) = false then 
   make new folder at desktop with properties {name:theNewFolderName} 
  else 
   display dialog "Did not create a folder because one already exists."

  end if 
 end tell 
else if theButton = "Maybe Later" then 
 display dialog "Trigger the script again when you are ready to build a folder."

else 
 display dialog "A folder has not been created."

end if

In Closing

As you can see, if/then statements can be tremendously useful when scripting. With the use of simple and complex if/then statements, your scripts can become infinitely flexible, allowing them to take specific action based on virtually any situation that might occur during processing. In fact, without the use of if/then statements and other powerful scripting techniques, such as repeat loops, certain types of workflows could just not be automated. Imagine trying to create a complex asset management system that uses AppleScript to move files around, without the use of if/then statements or repeat loops. It would be extremely difficult, to say the least, if not impossible. So, I encourage you to begin incorporating if/then statements into your scripts in order to automate more complex workflows, and make your scripts more robust.

Until next time, keep scripting!


Benjamin Waldie is president of Automated Workflows, LLC, a firm specializing in AppleScript and workflow automation consulting. In addition to his role as a consultant, Benjamin is an evangelist of AppleScript, and can frequently be seen presenting at Macintosh User Groups, Seybold Seminars, and MacWorld. For additional information about Benjamin, please visit http://www.automatedworkflows.com, or email Benjamin at applescriptguru@mac.com

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

OS X Server 4.1.3 - For OS X 10.10 Yosem...
Designed for OS X and iOS devices, OS X Server makes it easy to share files, schedule meetings, synchronize contacts, develop software, host your own website, publish wikis, configure Mac, iPhone,... Read more
pwSafe 4.1 - Secure password management...
pwSafe provides simple and secure password management across devices and computers. pwSafe uses iCloud to keep your password databases backed-up and synced between Macs and iOS devices. It is... Read more
Kodi 15.0.rc1 - Powerful media center to...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
Coda 2.5.11 - One-window Web development...
Coda is a powerful Web editor that puts everything in one place. An editor. Terminal. CSS. Files. With Coda 2, we went beyond expectations. With loads of new, much-requested features, a few surprises... Read more
Bookends 12.5.7 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Access the power of Bookends directly from Mellel, Nisus Writer Pro, or MS Word (... Read more
Maya 2016 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
RapidWeaver 6.2.3 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
MacFamilyTree 7.5.2 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Paragraphs 1.0.1 - Writing tool just for...
Paragraphs is an app just for writers. It was built for one thing and one thing only: writing. It gives you everything you need to create brilliant prose and does away with the rest. Everything in... Read more
BlueStacks App Player 0.9.21 - Run Andro...
BlueStacks App Player lets you run your Android apps fast and fullscreen on your Mac. Version 0.9.21: Note: Now requires OS X 10.8 or later running on a 64-bit Intel processor. Initial stable... Read more

Rage of Bahamut is Giving Almost All of...
The App Store isn't what it used to be back in 2012, so it's not unexpected to see some games changing their structures with the times. Now we can add Rage of Bahamut to that list with the recent announcement that the game is severely cutting back... | Read more »
Adventures of Pip (Games)
Adventures of Pip 1.0 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: ** ONE WEEK ONLY — 66% OFF! *** “Adventures of Pip is a delightful little platformer full of charm, challenge and impeccable... | Read more »
Divide By Sheep - Tips, Tricks, and Stre...
Who would have thought splitting up sheep could be so involved? Anyone who’s played Divide by Sheep, that’s who! While we’re not about to give you complete solutions to everything (because that’s just cheating), we will happily give you some... | Read more »
NaturalMotion and Zynga Have Started Tea...
An official sequel to 2012's CSR Racing is officially on the way, with Zynga and NaturalMotion releasing a short teaser trailer to get everyone excited. Well, as excited as one can get from a trailer with no gameplay footage, anyway. [Read more] | Read more »
Grab a Friend and Pick up Overkill 3, Be...
Overkill 3 is a pretty enjoyable third-person shooter that was sort of begging for some online multiplayer. Fortunately the begging can stop, because its newest update has added an online co-op mode. [Read more] | Read more »
Scanner Pro's Newest Update Adds Au...
Scanner Pro is one of the most popular document scanning apps on iOS, thanks in no small part to its near-constant updates, I'm sure. Now we're up to update number six, and it adds some pretty handy new features. [Read more] | Read more »
Heroki (Games)
Heroki 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: CLEAR THE SKIES FOR A NEW HERO!The peaceful sky village of Levantia is in danger! The dastardly Dr. N. Forchin and his accomplice,... | Read more »
Wars of the Roses (Games)
Wars of the Roses 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
TapMon Battle (Games)
TapMon Battle 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: It's time to battle!Tap! Tap! Tap! Try tap a egg to hatch a Tapmon!Do a battle with another tapmons using your hatched tapmons! *... | Read more »
Alchemic Dungeons (Games)
Alchemic Dungeons 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: ### Release Event! ### 2.99$->0.99$ for limited time! ### Roguelike Role Playing Game! ### Alchemic Dungeons is roguelike... | Read more »

Price Scanner via MacPrices.net

Seagate Backup Plus Drives Feature 200GB of C...
Seagate Technology plc has announced that its Backup Plus family of external storage offerings will now include 200GB of OneDrive cloud storage, a major added value, and the addition of Lyve’s photo... Read more
Canon PIXMA MG3620 Wireless Inkjet All-in-One...
Canon U.S.A., Inc. has announced the PIXMA MG3620 Wireless (1) Inkjet All-in-One (AIO) printer for high-quality photo and document printing. Built with convenience in mind for the everyday home user... Read more
July 4th Holiday Weekend 13-inch MacBook Pro...
Save up to $150 on the purchase of a new 2015 13″ Retina MacBook Pro at the following resellers this weekend. Shipping is free with each model: 2.7GHz/128GB MSRP $1299 2.7GHz/... Read more
27-inch 3.5GHz 5K iMac on sale for $2149, sav...
Best Buy has the 27″ 3.5GHz 5K iMac on sale for $2149.99. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary. Their price is $... Read more
Apple now offering refurbished 2015 11-inch...
The Apple Store is now offering Apple Certified Refurbished 2015 11″ MacBook Airs as well as 13″ MacBook Airs (the latest models), available for up to $180 off the cost of new models. An Apple one-... Read more
15-inch 2.5GHz Retina MacBook Pro on sale for...
Amazon.com has the 15″ 2.5GHz Retina MacBook Pro on sale for $2274 including free shipping. Their price is $225 off MSRP, and it’s the lowest price available for this model. Read more
Finally Safe To Upgrade To Yosemite’?
The reason I’ve held back from upgrading my MacBook Air from OS X 10.9 Mavericks to 10.10 Yosemite for nearly a year isn’t just procrastination. Among other bugs reported, there have been persistent... Read more
Logo Pop Free Vector Logo Design App For OS X...
128bit Technologies has released of Logo Pop Free 1.2 for Mac OS X, a vector based, full-fledged, logo design app available exclusively on the Mac App Store for the agreeable price of absolutely free... Read more
21-inch 1.4GHz iMac on sale for $999, save $1...
B&H Photo has new 21″ 1.4GHz iMac on sale for $999 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Best Buy has the 21″ 1.4GHz iMac on sale for $999.99 on their... Read more
16GB iPad mini 3 on sale for $339, save $60
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $339 including free shipping plus NY tax only. Their price is $60 off MSRP. Read more

Jobs Board

Mobile Payments Counsel, *Apple* Pay (digit...
**Job Summary** Apple is looking for an atto ey to join Apple 's Legal Department to support Apple Pay. **Key Qualifications** 4+ years of relevant experience Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** The ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store which delivers Read more
Partner Marketing Manager, Merchant- *Apple*...
**Job Summary** The Apple Pay partner marketing team is looking for a marketing manager to develop and drive US marketing programs with our merchant partners. The right Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
Program Manger, WW *Apple* Direct Fulfillme...
**Job Summary** We are seeking a business analyst to work within our Worldwide Apple Direct Fulfillment Operations team. This role will work closely with related program Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.