Get/Set property value in custom getter/setter

Coding Python Support
1

Hello, everyone.
I started to code my first add-on and, probably because I can find good complete step by step and up-to-date tutorials, I accumulate simple problems that I take hours to understand.
Last in date, I have define 2 customs properties for MovieClip type to use for my add-on, CtFStart and CtFEnd, each one editable in the add-on custom panel. My concern is that CtFStart must always be lower than CtFEnd. So I looked to bpy.props Blender API references, read the «Get/Set Example» and apply to my situation, thinking I could use a custom setter method to check value before assigning it. I first created a setter method supposed to do exactly what the original does as write in the Blender references:

def set_start_frame(self, val):
    '''check Start frame new Value'''
    self['CtFStart'] = val

# Add to movieclip type the CtFStart property
bpy.types.MovieClip.CtFStart =bpy.props.IntProperty(
        name = "First frame",
        description = "…",
        default = 0,
        min = 0, 
        set=set_start_frame)

So the problem is that don’t work and I can’t understand why:confused:. When I increase CtFStart value in the UI and release the mouse button, CtFStart value is still 0. I have tried to assign value like that:

def set_start_frame(self, val):
    '''check Start frame new Value'''
    self.CtFStart = val

Wich result in infinite recursive call to the setter.

I have tried to print(val) before assign it to self[‘CtFStart’], and it realy seams to be the good value. Then, I tried to print self[‘CtFStart’] and get an error:«KeyError: ‘bpy_struct[key]: key “CtFStart” not found’».So I search and all answers I find still says to access it like I do in the setter function (unless I miss a detail?).

By curiosity, in set_start_frame(self,val) function, I also tried to search CtFStart in self.rna_type and find find it at self.rna_type.CtFStart and self.rna_type.properties[‘CtFStart’], but I still can’t get or set the value.

So I would be happy if some of you can enligthen me.

2

Wrap two your properties to property group and use update method. Something like that:


class myVars(bpy.types.PropertyGroup):
    fStart = bpy.props.IntProperty(
        name = 'start',
        update = updateVars
    )
    fEnd = bpy.props.IntProperty(
        name = 'end',
        update = updateVars
    )
)
def updateVars(self, context):
    if self.fEnd < self.fStart:
        self.fEnd = self.fStart + 1
1 Like
3

Thanks Korchy, You’ve been a geat help.

For the record:
Using a PropertyGroup don’t change anything to my problem, but using a «update» function rather than a «set» function, as you suggest in your code, have been working. The only matter is that assigning a new value like you do «self.fEnd = self.fStart + 1» result in a recursive call, so I use rather «self[‘fEnd’] = self.fStart + 1» who works well this time.

P.S.: How do we set the thread as RESOLVED?