5. How to show “on” or “off” icons for calculated boolean fields?

In the previous chapter, How to enable filtering on calculated fields? you added a boolean field.:

def is_very_benevolent(self, obj):
    return obj.benevolence_factor > 75

Which looks like this

The is_very_benevolent field shows the string True and False, unlike the builtin BooleanFields which show an on and off indicator. To fix this, you add a boolean attribute on your method. You final modeladmin looks like this:

@admin.register(Hero)
class HeroAdmin(admin.ModelAdmin):
    list_display = ("name", "is_immortal", "category", "origin", "is_very_benevolent")
    list_filter = ("is_immortal", "category", "origin", IsVeryBenevolentFilter)

    def is_very_benevolent(self, obj):
        return obj.benevolence_factor > 75

    is_very_benevolent.boolean = True

And your admin looks like this