Structured Problem Solving

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Structured Problem Solving

• The SmallTalk Environment

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The First Window

• When this window appears, you are ready to start
  your Smalltalk session.
• Do not do anything to the text in this window, it
  is just information.
• Click on
• File New Workspace

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SummaryThe SmallTalk Workspace
Starting a New workspace Select File New
Workspace Adding Text Type in, it is a text
editor. Saving Select File Save Opening Select
File Open Executing Select the Text, right
click, Do it
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Messages
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A New Object
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A New Object
Tony1 is the name of the object. We use this
name to address it.
TonysPie is the label at the top of the Grid.
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Longer Programs
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Longer Programs
Note the full stops at the end of each message.
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Repeating
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Repeating
Note the loop structure 4 timesRepeat

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Repeating
Note the loop contents Message1 . Message2.
Message3 Separated by full stops.
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Creating New Objects

• Identifying Attributes Protocols

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Attributes

• Names for Attributes will
• Begin with a lower case letter
• Contain no spaces
• e.g. customerName
• numberOfRecords
• colour

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Names for Protocols

• Names for Protocols will
• Begin with a lower case letter
• Contain no spaces
• e.g. reserveVideo
• turnRight
• red

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Messages 1

• Each message which sets an attribute value has
  the structure
• attribute value
• For example to set a customer name we would send
  the message
• customerName Tony
• The message to an object called customer1 would
  be
• customer1 customerName Tony

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Messages 2

• Each message which requests an attribute value as
  a reply should be given the same name as the
  attribute name.
• for example
• customerName
• is the message which requests the value of an
  objects customerName
• Customer1 customerName

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Student Database

• A simple database is required to store a student
  ID number, their year of study and their current
  modules.
• We will wish to be able to send messages to the
  objects to increment the year of study, and
  change current modules.
• We will also need to interrogate the object to
  find out the year of study.

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Student Database Attributes

• The database will consist of a class of objects
  called student
• These objects will have the following attributes
• studentID
• yearofStudy
• currentModule1
• currentModule2

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Student Database Protocol

• changeYear
• adds 1 to the current year
• currentModule1
• changes currentModule1
• currentModule2
• changes currentModule2
• yearofStudy
• requests the current year of study

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Example

• The following messages are sent
• changeYear
• currentModule1 M20001A
• currentModule2 M20002B

• OBJECT Student1
• Class of Object Student
• studentID 12345678
• yearofStudy 2
• currentModule1 M10001A
• currentModule2 M10002B
• Protocol
• changeYear, currentModule1, currentModule2 ,
  yearofStudy

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Example

• The following message is sent
• yearofStudy
• The object responds with
• 3

• OBJECT Student1
• Class of Object Student
• studentID 12345678
• yearofStudy 3
• currentModule1 M20001A
• currentModule2 M20002B
• Protocol
• changeYear, currentModule1, currentModule2 ,
  yearofStudy