Question

这是代码

[EvoScrollBarTagView initWithScrollView:self.listTableView
                                withTagView:[TagView new]
                                  didScroll:
                        ^(id scrollBarTagView, TagView *tagView, CGFloat offset) {

                          [scrollBarTagView showTagViewAnimation];
                          ........

我的困惑是为什么scrollBarTagView（id-type）可以调用我的EvoScrollBarTagView.h中的方法或属性。参数scrollBarTagView s type is id, not declared as the EvoScrollBarTagView的实例对象，有人可以告诉我原因，非常感谢...

Answer 1

如Objective-C is a dynamic language中所述：

id类型定义了一个通用对象指针。可以使用id 声明变量时，但是丢失了编译时的信息对象。

所以它并不意味着scrollBarTagView可以调用任何方法，这意味着它将成功编译。如果未实现引用的方法，则应用程序将在运行时崩溃。

Answer 2

这是fit - 动态类型的一部分。您可以尝试将任何消息（编译器在此代码中知道的消息）发送到类型>>> from sklearn.preprocessing import Binarizer >>> Binarizer().fit_transform(y) Warning (from warnings module): File "C:\Python34\lib\site-packages\sklearn\utils\validation.py", line 386 DeprecationWarning) DeprecationWarning: Passing 1d arrays as data is deprecated in 0.17 and willraise ValueError in 0.19. Reshape your data either using X.reshape(-1, 1) if your data has a single feature or X.reshape(1, -1) if it contains a single sample. Warning (from warnings module): File "C:\Python34\lib\site-packages\sklearn\utils\validation.py", line 386 DeprecationWarning) DeprecationWarning: Passing 1d arrays as data is deprecated in 0.17 and willraise ValueError in 0.19. Reshape your data either using X.reshape(-1, 1) if your data has a single feature or X.reshape(1, -1) if it contains a single sample. array([[1, 0, 1, 0]]) >>> b = Binarizer() >>> b.transform(y) Warning (from warnings module): File "C:\Python34\lib\site-packages\sklearn\utils\validation.py", line 386 DeprecationWarning) DeprecationWarning: Passing 1d arrays as data is deprecated in 0.17 and willraise ValueError in 0.19. Reshape your data either using X.reshape(-1, 1) if your data has a single feature or X.reshape(1, -1) if it contains a single sample. array([[1, 0, 1, 0]])的表达式，而不会出现任何编译器错误或警告。

在块iOS中使用参数type-of id

2 个答案: