使用 arcgis 中的 arcpy 在脚本验证中从 Fc 列表中列出参数中的字段

Question

我正在尝试在脚本工具验证中列出功能 class 列表中的字段。 首先用户从列表中选择数据框，然后 FC 在下一个框中填充，FC 的字段在下一个框中填充。 我有代码可以填充 FC 列表并且工作正常。 但在那之后我正在尝试从 FC 列出字段并得到错误。

这是代码

import arcpy
class ToolValidator(object):
  """Class for validating a tool's parameter values and controlling
  the behavior of the tool's dialog."""

  def __init__(self):
    """Setup arcpy and the list of tool parameters."""
    self.params = arcpy.GetParameterInfo()

  def initializeParameters(self):
    """Refine the properties of a tool's parameters.  This method is
    called when the tool is opened."""
    try:   # this works
        mxd = arcpy.mapping.MapDocument('CURRENT')
        dflist = [df.name for df in arcpy.mapping.ListDataFrames(mxd)]
        self.params[1].filter.type = "ValueList"
        self.params[1].filter.list = dflist
        del mxd
    except:
        arcpy.AddError("\nMust run this tool in ArcMap, not ArcCatalog")

    self.params[2].enabled = True

    return

  def updateParameters(self):
    """Modify the values and properties of parameters before internal
    validation is performed.  This method is called whenever a parameter
    has been changed."""
    mxd = arcpy.mapping.MapDocument('CURRENT')

    if self.params[1].value:
        self.params[2].enabled = True

        df = arcpy.mapping.ListDataFrames(mxd, self.params[1].value)[0]
        # creates an empty dictionary
        if df:
            layerList = [lyr.name for lyr in arcpy.mapping.ListLayers(df) if not lyr.isGroupLayer]
            uniqueList = list(set(layerList))
            uniqueList.sort()
            self.params[2].filter.list = uniqueList


# Up to this it working and problem is from below code


    if self.params[2].value:
        self.params[3].enabled = True

        df = str(self.params[1].value)   
        lyrList = arcpy.mapping.ListLayers(mxd, "", df)  
        for lyr in lyrList:  
            if lyr.supports("dataSource") and lyr.name == str(self.params[2].value):  
                for field in arcpy.ListFields(lyr.dataSource):  
                    uniqueList = list(set(field))
                    uniqueList.sort()
                    self.params[3].filter.list = uniqueList            


    return

  def updateMessages(self):
    """Modify the messages created by internal validation for each tool
    parameter.  This method is called after internal validation."""
    return