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6a17a60ae2
Add new register_function method when not using decorator Wrap function call in try block to catch and report errors
90 lines
2.7 KiB
Python
90 lines
2.7 KiB
Python
import string
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from qgis._core import *
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def register_function(function, arg_count, group, usesgeometry=False, **kwargs):
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"""
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Register a Python function to be used as a expression function.
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Functions should take (values, feature, parent) as args:
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Example:
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def myfunc(values, feature, parent):
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pass
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They can also shortcut naming feature and parent args by using *args
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if they are not needed in the function.
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Example:
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def myfunc(values, *args):
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pass
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Functions should return a value compatible with QVariant
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Eval errors can be raised using parent.setEvalErrorString("Error message")
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:param function:
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:param arg_count:
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:param group:
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:param usesgeometry:
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:return:
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"""
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class QgsExpressionFunction(QgsExpression.Function):
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def __init__(self, func, name, args, group, helptext='', usesgeometry=False):
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QgsExpression.Function.__init__(self, name, args, group, helptext, usesgeometry)
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self.function = func
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def func(self, values, feature, parent):
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try:
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return self.function(values, feature, parent)
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except Exception as ex:
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parent.setEvalErrorString(ex.message)
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helptemplate = string.Template("""<h3>$name function</h3><br>$doc""")
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name = kwargs.get('name', function.__name__)
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helptext = function.__doc__ or ''
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helptext = helptext.strip()
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if arg_count == 0 and not name[0] == '$':
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name = '${0}'.format(name)
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if QgsExpression.isFunctionName(name):
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if not QgsExpression.unregisterFunction(name):
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raise TypeError("Unable to unregister function")
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function.__name__ = name
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helptext = helptemplate.safe_substitute(name=name, doc=helptext)
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f = QgsExpressionFunction(function, name, arg_count, group, helptext, usesgeometry)
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# This doesn't really make any sense here but does when used from a decorator context
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# so it can stay.
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register = kwargs.get('register', True)
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if register:
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QgsExpression.registerFunction(f)
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return f
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def qgsfunction(args, group, **kwargs):
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"""
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Decorator function used to define a user expression function.
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Example:
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@qgsfunction(2, 'test'):
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def add(values, feature, parent):
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pass
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Will create and register a function in QgsExpression called 'add' in the
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'test' group that takes two arguments.
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or not using feature and parent:
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Example:
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@qgsfunction(2, 'test'):
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def add(values, *args):
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pass
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"""
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def wrapper(func):
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usesgeometry = kwargs.get('usesgeometry', False)
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return register_function(func, args, group, usesgeometry, **kwargs)
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return wrapper
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