here - Stefan-Marr.de

5.3. The OMOP By Example
current :
Domain
initialDomainForNewObjects
main()
new
set: #foo
cell:
Cell
ImmutableDomain
evaluateEnforced: [cell set: #bar]
enforced
adopt: cell
set: #bar
→ reqExecOf: #set on: cell with: #bar
set: #bar
write: #bar toField: 1 of: cell
ImmutabilityError
Figure 5.3.: Enforcing Immutability with the OMOP. This sequence diagram depicts
a typical interaction between the application and a domain. The main program
starts in unenforced execution mode and creates a cell object. Since it has not
specified any domain as yet, it executes in the context of the standard, i. e., uncustomized
domain. During the creation of the cell object the current domain is
used to determine its initial owner. The main program continues to set an initial
value for the cell (#foo) and then requests the immutable domain to adopt the
cell object. This completes the initialization of the program and it enables the enforced
execution mode. When the main program now attempts to execute the setter
method on the cell, the immutable domain will reify the execution. However,
immutability does not interfere with method execution and thus, the request is
granted and the setter is executed. Eventually, the setter will attempt to write the
object field of the cell, which the immutable domain specifies a custom policies
for. Thus, the write attempt results in an invocation of the #write:toField:of:
intercession handler, which signals a violation of immutability and does not perform
the state change.
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