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(Quick Reference) # 6.3.6 Modification Checking - Reference Documentation Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari Version: 2.3.8 ## 6.3.6 Modification Checking Once you have loaded and possibly modified a persistent domain class instance, it isn't straightforward to retrieve the original values. If you try to reload the instance using get Hibernate will return the current modified instance from its Session cache. Reloading using another query would trigger a flush which could cause problems if your data isn't ready to be flushed yet. So GORM provides some methods to retrieve the original values that Hibernate caches when it loads the instance (which it uses for dirty checking). #### isDirty You can use the isDirty method to check if any field has been modified:

    def airport = Airport.get(10)
    assert !airport.isDirty()airport.properties = params
    if (airport.isDirty()) {
       // do something based on changed state
    }
`isDirty()` does not currently check collection associations, but it does check all other persistent properties and associations. You can also check if individual fields have been modified:

    def airport = Airport.get(10)
    assert !airport.isDirty()airport.properties = params
    if (airport.isDirty('name')) {
       // do something based on changed name
    }
#### getDirtyPropertyNames You can use the getDirtyPropertyNames method to retrieve the names of modified fields; this may be empty but will not be null:

    def airport = Airport.get(10)
    assert !airport.isDirty()airport.properties = params
    def modifiedFieldNames = airport.getDirtyPropertyNames()
    for (fieldName in modifiedFieldNames) {
       // do something based on changed value
    }
#### getPersistentValue You can use the getPersistentValue method to retrieve the value of a modified field:

    def airport = Airport.get(10)
    assert !airport.isDirty()airport.properties = params
    def modifiedFieldNames = airport.getDirtyPropertyNames()
    for (fieldName in modifiedFieldNames) {
        def currentValue = airport."$fieldName"
        def originalValue = airport.getPersistentValue(fieldName)
        if (currentValue != originalValue) {
            // do something based on changed value
        }
    }
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