Question

我有一个以svg html元素（<svg></svg>）为参数的打字稿类：

export class MyClass extends Base {
  private svg: SVGSVGElement;
  constructor(svg: SVGSVGElement) {
  }
}

您将使用javascript这样调用它：

new MyClass(document.getElementById("mySVGElement"));

问题是，如果我传递的不是svg元素，则什么也不会发生。如果传递的html元素不是svg，如何抛出错误？喜欢：

constructor(svg: SVGSVGElement) {
  if (svg not svg) {
    //throw error
  }
}

Answer 1

--------------------------------------------------------------------------- ValueError Traceback (most recent call last) <ipython-input-78-0358d9976c72> in <module> ----> 1 gv.Polygons(gdf, kdims=['year'], vdims=['pre_anom']).opts(width=600, height=600, tools=['hover'], 2 colorbar=True, cmap='RdBu', color_index='pre_anom', 3 symmetric=True, toolbar='above', line_color='white') ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/geoviews/element/geo.py in __init__(self, data, kdims, vdims, **kwargs) 98 elif isinstance(data, _Element): 99 kwargs['crs'] = data.crs --> 100 super(_Element, self).__init__(data, kdims=kdims, vdims=vdims, **kwargs) 101 102 ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/holoviews/element/path.py in __init__(self, data, kdims, vdims, **params) 217 else: 218 params['vdims'] = vdims --> 219 super(Contours, self).__init__(data, kdims=kdims, **params) 220 if params.get('level') is not None: 221 with disable_constant(self): ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/holoviews/element/path.py in __init__(self, data, kdims, vdims, **params) 90 91 super(Path, self).__init__(data, kdims=kdims, vdims=vdims, ---> 92 datatype=datatype, **params) 93 94 ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/holoviews/core/data/__init__.py in __init__(self, data, kdims, vdims, **kwargs) 210 datatype=kwargs.get('datatype')) 211 (data, self.interface, dims, extra_kws) = initialized --> 212 super(Dataset, self).__init__(data, **dict(kwargs, **dict(dims, **extra_kws))) 213 self.interface.validate(self, validate_vdims) 214 ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/holoviews/core/dimension.py in __init__(self, data, kdims, vdims, **params) 994 params['cdims'] = {d if isinstance(d, Dimension) else Dimension(d): val 995 for d, val in params['cdims'].items()} --> 996 super(Dimensioned, self).__init__(data, **params) 997 self.ndims = len(self.kdims) 998 cdims = [(d.name, val) for d, val in self.cdims.items()] ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/holoviews/core/dimension.py in __init__(self, data, id, plot_id, **params) 650 params['group'] = long_name 651 --> 652 super(LabelledData, self).__init__(**params) 653 if not util.group_sanitizer.allowable(self.group): 654 raise ValueError("Supplied group %r contains invalid characters." % ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/param/parameterized.py in __init__(self, **params) 2029 self.param._generate_name() 2030 -> 2031 self.param._setup_params(**params) 2032 object_count += 1 2033 ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/param/parameterized.py in override_initialization(self_, *args, **kw) 808 original_initialized=parameterized_instance.initialized 809 parameterized_instance.initialized=False --> 810 fn(parameterized_instance,*args,**kw) 811 parameterized_instance.initialized=original_initialized 812 return override_initialization ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/param/parameterized.py in _setup_params(self_, **params) 950 self.param.warning("Setting non-parameter attribute %s=%s using a mechanism intended only for parameters",name,val) 951 # i.e. if not desc it's setting an attribute in __dict__, not a Parameter --> 952 setattr(self,name,val) 953 954 @classmethod ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/param/__init__.py in __set__(self, obj, val) 1217 def __set__(self,obj,val): 1218 """Set to the given value, raising an exception if out of bounds.""" -> 1219 self._check_bounds(val) 1220 super(List,self).__set__(obj,val) 1221 ~/.conda/envs/anaconda3.6/lib/python3.6/site-packages/param/__init__.py in _check_bounds(self, val) 1236 if min_length is not None and max_length is not None: 1237 if not (min_length <= l <= max_length): -> 1238 raise ValueError("%s: list length must be between %s and %s (inclusive)"%(self._attrib_name,min_length,max_length)) 1239 elif min_length is not None: 1240 if not min_length <= l: ValueError: kdims: list length must be between 2 and 2 (inclusive)是上课的权利吗？ SVGSVGElement

Answer 2

在打字稿中，document.getElementById返回HTMLElement | null（请参阅here），并且无法将HTMLElement转换为SVGSVGElement（请参阅here并搜索“ HTMLElement”）。

这意味着您必须“假设”构造函数参数内的正确类型，并“检查”构造函数体内的正确性。

export class MyClass extends Base {
  private svg: SVGSVGElement;

  constructor(svg: SVGSVGElement) {
    if (svg instanceof SVGSVGElement === false) {
      throw Error()
    }

    // ...
  }
}

关于更改document.getElementById here的行为，人们进行了积极的讨论。

Answer 3

您可以将参数类型设置为'any'，然后检查svgsvgelement。

虽然可能不是最好的方法。

Answer 4

您可以使用file.type检查文件的MIME类型

https://developer.mozilla.org/en-US/docs/Web/API/File/type

您可以像这样简单地进行支票

if (!file.type == "image/svg+xml"){
   throw new Error('FileType is invalid');
}

Answer 5

new MyClass(document.getElementById("mySVGElement"));

应引起编译器错误，因为Document.getElementById返回HTMLElement。因此，您在编译时已经具有类型安全性。但是，如果仍然需要在运行时强制执行此操作，那么Stefan's answer应该是在运行时进行检查的规范方法。

Answer 6

export class MyClass extends Base {
    constructor(svg: SVGSVGElement) {
        if (svg instanceof SVGElement !== true) {
            throw new Error('Invalid element passed to constructor!')
        }
    }
}

这就是stefan-wullems所谈论的代码。

如果传递给类的元素不是svg（打字稿），则会引发错误

6 个答案: