Derived settable attributes
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Derived attributes use and OCL expression to calculate the presentation of another attribute.
=== What Are These? ===
* Derived attributes use an OCL expression to calculate the presentation of another attribute.


Derived '''settable''' attributes use EAL to do the reverse, i.e. setting the source attribute from the entered value.
* Derived '''settable''' attributes use EAL to do the reverse, i.e. setting the source attribute from the entered value. The user input is in the '''vInputParameter''' variable.
This opens up special handling of user input and "user shortcuts" in the UI - for example, accepting only a number as a time entry.


This opens up special handling of user input and "user shortcuts" in the UI. For example accepting only a number as a time entry.
=== Example with Time (DateTime) and Decimal ===
This example uses ''FromTimeText'', ''HoursText,'' and ''ToTimeText'' for user input, but only '''FromTime''' and '''Hours''' for storing information in the database.


=== Example with Time (DateTime) and Decimal ===
This special handling makes user input much simpler because it handles the user's need to change any of the three values, updating the others behind the scenes.
This example uses ''FromTimeText'', ''HoursText'' and ''ToTimeText'' for user input, but only '''FromTime''' and '''Hours''' for storing information in the database.
[[File:TimeSpent class example.png|thumb|none]]
[[File:TimeSpent class example.png|thumb|none]]
 
* '''/Date''' is a derived attribute for easy access to a neighboring class containing the date in DateTime format.
'''/Date''' is a derived attribute for easy access to a neighboring class' containing the date in DateTime format.
* '''/EffectiveToTime''' is a derived attribute used as a companion to the FromTime, again for symmetry in accessing the information.
 
'''/EffectiveToTime''' is a derived attribute used a companion to the FromTime, again for symmetry in access the information.
 
Support function '''StringToTime()'''
Support function '''StringToTime()'''


To help the other function with conversion, a help function like this was created
To help the other function with conversion, a help function like this was created:


  if aText.length <= 2 then
  if aText.length <= 2 then
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   DateTime.Parse('1900-01-01 ' + aText)
   DateTime.Parse('1900-01-01 ' + aText)
  endif
  endif
Note the addition of ''':00''' to the text if it is short, this help the user out if entering just the hour part.
* Note the addition of "''':00'''" to the text if it is short. This helps the user out of entering just the hour part.
* '1900-01-01' is an ugly hack to prevent storing the current date as part of the time entry. It would still work, but this is slightly better.


'1900-01-01' is an ugly hack to prevent storing the current date as part of the time entry. It would work anyhow, but this is slightly better.
===== Property Inspector =====
 
Below is the property inspector setting for a derived settable attribute. Note the AttributeMode and then the OCL and OclSet code.
===== Property inspector =====
Below is the property inspector setting for an derived settable attribute. Note the AttributeMode and then the Ocl and OclSet code.
[[File:DerivedSettable property inspector.png|none|thumb|382x382px]]
[[File:DerivedSettable property inspector.png|none|thumb|382x382px]]


===== /FromTimeText: String? =====
===== /FromTimeText: String? =====
OCL
''OCL''


  if self.FromTime.notNull then
  if self.FromTime.notNull then
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  endif
  endif


EAL (OclSet)
''EAL (OclSet)''


  self.FromTime := self.StringToTime(vInputParameter)
  self.FromTime := self.StringToTime(vInputParameter)
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'''/HoursText: String?'''
'''/HoursText: String?'''


OCL
''OCL''


In Sweden we use comma, not the dot as a decimal separator. Hard coded replacement.
In Sweden, we use the comma instead of the dot as a decimal separator. Hard-coded replacement:


  self.Hours.ToString('N2').Replace('.', ',')
  self.Hours.ToString('N2').Replace('.', ',')


EAL (OclSet)
''EAL (OclSet)''


Enable use of both comma and dot as decimal separator. Round to 2 decimals to avoid fractions from the web browser double type. (JavaScript don't have Decimals, only Float)
Enable the use of both the comma and dot as decimal separators. Round to 2 decimals.


  self.Hours := Decimal.Parse(vInputParameter.Replace(',', '.')).Round(2)
  self.Hours := Decimal.Parse(vInputParameter.Replace(',', '.')).Round(2)
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'''/ToTimeText: String?'''
'''/ToTimeText: String?'''


The to-time is all calculated and only exist when showing and entering values.
The to-time is all calculated and only exists when showing and entering values.


OCL
''OCL''


  if self.FromTime.notNull then
  if self.FromTime.notNull then
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  endif
  endif


EAL (OclSet)
''EAL (OclSet)''


Handle both setting '''Hours''' or '''FromTime''' based on what information is already present.
Handle both setting '''Hours''' or '''FromTime''' based on what information is already present.
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   0
   0
  endif
  endif
    [[Category:MDriven Designer]]
See also:
[[Derived attributes & associations]]
[[Derived settable associations]]
{{Edited|July|12|2024}}
[[Category:TOC]]

Latest revision as of 13:46, 26 March 2024

What Are These?

  • Derived attributes use an OCL expression to calculate the presentation of another attribute.
  • Derived settable attributes use EAL to do the reverse, i.e. setting the source attribute from the entered value. The user input is in the vInputParameter variable.

This opens up special handling of user input and "user shortcuts" in the UI - for example, accepting only a number as a time entry.

Example with Time (DateTime) and Decimal

This example uses FromTimeText, HoursText, and ToTimeText for user input, but only FromTime and Hours for storing information in the database.

This special handling makes user input much simpler because it handles the user's need to change any of the three values, updating the others behind the scenes.

TimeSpent class example.png
  • /Date is a derived attribute for easy access to a neighboring class containing the date in DateTime format.
  • /EffectiveToTime is a derived attribute used as a companion to the FromTime, again for symmetry in accessing the information.

Support function StringToTime()

To help the other function with conversion, a help function like this was created: 

if aText.length <= 2 then
  DateTime.Parse('1900-01-01 ' + aText + ':00')
else
  DateTime.Parse('1900-01-01 ' + aText)
endif
  • Note the addition of ":00" to the text if it is short. This helps the user out of entering just the hour part.
  • '1900-01-01' is an ugly hack to prevent storing the current date as part of the time entry. It would still work, but this is slightly better.
Property Inspector

Below is the property inspector setting for a derived settable attribute. Note the AttributeMode and then the OCL and OclSet code.

DerivedSettable property inspector.png
/FromTimeText: String?

OCL 

if self.FromTime.notNull then
  self.FromTime.formatDateTime('HH:mm')
else
  String.nullValue
endif

EAL (OclSet) 

self.FromTime := self.StringToTime(vInputParameter)

/HoursText: String?

OCL

In Sweden, we use the comma instead of the dot as a decimal separator. Hard-coded replacement: 

self.Hours.ToString('N2').Replace('.', ',')

EAL (OclSet)

Enable the use of both the comma and dot as decimal separators. Round to 2 decimals. 

self.Hours := Decimal.Parse(vInputParameter.Replace(',', '.')).Round(2)

/ToTimeText: String?

The to-time is all calculated and only exists when showing and entering values.

OCL 

if self.FromTime.notNull then
  self.FromTime.AddHours(self.Hours.Value.ToDouble).formatDateTime('HH:mm')
else
  String.nullValue
endif

EAL (OclSet)

Handle both setting Hours or FromTime based on what information is already present. 

if self.FromTime.notNull then
  self.Hours := Decimal.Create(self.StringToTime(vInputParameter).Subtract(self.FromTime).TotalHours)
else
  self.FromTime := self.StringToTime(vInputParameter).AddHours(-self.Hours.ToDouble);
  0
endif

See also:

Derived attributes & associations

Derived settable associations

This page was edited 47 days ago on 03/26/2024. What links here
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