Google AppMaker日期验证

Question

如何在此处进行日期验证，以便当用户输入结束日期小于开始日期时，会向用户提示错误？ AppMaker是否有内置功能？谢谢分享！

Answer 1

如果要限制数据模型的输入，可以使用数据模型的高级部分。

您还可以通过事件部分或数据验证部分进行数据验证。使用第一个脚本来实现小脚本，使用第二个脚本将规则硬编码到应用程序中。

In [1]: class MyObject:
            pass

In [2]: obj = MyObject()

In [3]: # now lets try deleting the object
        # First, create a weak reference to obj, so we can know when it is truly deleted.
        from weakref import ref
        from sys import getrefcount
        r = ref(obj)
        print("the weak reference looks like", r)
        print("it has a reference count of", getrefcount(r()))
        # this prints a ref count of 2 (1 for obj and 1 because getrefcount
        # had a reference to obj)
        del obj
        # since obj was the only strong reference to the object, it should have been 
        # garbage collected now.
        print("the weak reference looks like", r)

the weak reference looks like <weakref at 0x7f29a809d638; to 'MyObject' at 0x7f29a810cf60>
it has a reference count of 2
the weak reference looks like <weakref at 0x7f29a809d638; dead>

In [4]: # lets try again, but this time we won't print obj, will just do "obj"
        obj = MyObject()

In [5]: print(getrefcount(obj))
        obj

2
Out[5]: <__main__.MyObject at 0x7f29a80a0c18>

In [6]: # note the "Out[5]". This is a second reference to our object
        # and will keep it alive if we delete obj
        r = ref(obj)
        del obj
        print("the weak reference looks like", r)
        print("with a reference count of:", getrefcount(r()))

the weak reference looks like <weakref at 0x7f29a809db88; to 'MyObject' at 0x7f29a80a0c18>
with a reference count of: 7

In [7]: # So what happened? It's that Out[5] that is keeping the object alive.
        # if we clear our Out variables it should go away...
        # As it turns out Juypter keeps a number of its own variables lying around, 
        # so we have to reset pretty everything.

In [8]: def my_reset(*varnames):
            """
            varnames are what you want to keep
            """
            globals_ = globals()
            to_save = {v: globals_[v] for v in varnames}
            to_save['my_reset'] = my_reset  # lets keep this function by default
            del globals_
            get_ipython().magic("reset")
            globals().update(to_save)

        my_reset('r') # clear everything except our weak reference to the object
        # you would use this to keep "thing" around.

Once deleted, variables cannot be recovered. Proceed (y/[n])? y

In [9]: print("the weak reference looks like", r)

the weak reference looks like <weakref at 0x7f29a809db88; dead>