pyobjc索引访问器方法与范围 [英] pyobjc indexed accessor method with range

问题描述

我试图在Python中为我的模型类实现一个索引访问器方法，如 KVC指南。我想使用可选的远程方法，为了性能原因一次加载多个对象。该方法接受一个指向C阵列缓冲区的指针，我的方法需要该指针将对象复制到其中。我试过像下面的东西，这不工作。如何实现这个？

  @ objc.accessor＃我也试过@ objc.signature（'v @：o ^ @'）
 def getFoos_range_（self，range）：
 return self._some_array [range.location：range.location + range.length] 
  

编辑：我终于找到了类型编码引用。读完之后，我尝试过：

  @ objc.signature（'v @：N ^ @@'）
 def getFoos_range_（self，buf，range）：
  

但这看起来不工作。第一个参数应该是一个指向C数组的指针，但是长度在运行时之前是未知的，所以我不知道如何构造正确的类型编码。我尝试了'v @：N ^ [1000 @] @'只是看到，也没有工作。

我的模型对象绑定到驱动表视图的NSArrayController的contentArray。它似乎根本不是调用这个方法，也许是因为它期望一个不同的签名，而不是桥提供的。有任何建议吗？

解决方案

此方法的正确装饰是：

  @ objc.signature（'v @：o ^ @ {_ NSRange = QQ} ）
  

NSRange 不是一个对象，一个结构体，不能简单地指定为 @ ;您需要包括成员 ¹ 。

不幸的是，这不是结束。在对PyObjC源进行了大量的实验和运算之后，我终于知道为了让这个方法起作用，你还需要为该签名指定冗余的方法的元数据。

这是使用函数 objc.registerMetaDataForSelector 完成的。 ：

  objc.registerMetaDataForSelector（bSUPERCLASSNAME，
bgetKey：range：，
 dict （retval = dict（type = objc._C_VOID），
 arguments = {
 2 + 0：dict（type_modifier = objc._C_OUT，
 c_array_length_in_arg = 2 + 1），
 2 + 1：dict（type = b'{_ NSRange = II}'，
 type64 = b'{_ NSRange = QQ}'）
} 
）
）$ b b 

使用此函数的示例和一些详细信息可以在 test_metadata_py.py （和附近的 test_metadata * .py 文件）。





NB 必须在 c $ c> get< Key>：range： for，并且该函数需要在类定义结束之前的某个时间被调用（但是在类语句本身似乎都工作）。

我基于元数据元数据 NSArray getObjects：range：在基金会PyObjC.bridgesupport文件 ² ，并通过参考Apple的 BridgeSupport联机帮助页。

有了这个功能，还值得注意的是定义方法的最简单的方法是（至少，IMO）：

  @ objc.signature（'v @：o ^ @ {_NSRange = QQ}'）
 def get<＃Key＃> _range_（self，buf，inRange）：
 #NSLog（uget<＃Key＃>）
 return self。<＃Key＃> .getObjects_range_（buf，inRange）
  

数组的内置 getObjects：range：。

---

在32位Python上， QQ 意味着两个 unsigned long long II ，表示两个 unsigned int s

2：位于（系统/库/框架） /Python.framework/Versions/2.6/Extras/lib/python/PyObjC/Foundation/PyObjC.bridgesupport

I'm trying to implement an indexed accessor method for my model class in Python, as per the KVC guide. I want to use the optional ranged method, to load multiple objects at once for performance reasons. The method takes a pointer to a C-array buffer which my method needs to copy the objects into. I've tried something like the following, which doesn't work. How do I accomplish this?

@objc.accessor    # i've also tried @objc.signature('v@:o^@')
def getFoos_range_(self, range):
    return self._some_array[range.location:range.location + range.length]

Edit: I finally found the type encodings reference after Apple moved all the docs. After reading that, I tried this:

@objc.signature('v@:N^@@')
def getFoos_range_(self, buf, range):

but this didn't appear to work either. The first argument is supposed to be a pointer to a C-array, but the length is unknown until runtime, so I didn't know exactly how to construct the correct type encoding. I tried 'v@:N^[1000@]@' just to see, and that didn't work either.

My model object is bound to the contentArray of an NSArrayController driving a table view. It doesn't appear to be calling this method at all, perhaps because it expects a different signature than the one the bridge is providing. Any suggestions?

解决方案

You were close. The correct decorator for this method is:

@objc.signature('v@:o^@{_NSRange=QQ}')

NSRange is not an object, but a struct, and can't be specified simply as @; you need to include the members¹.

Unfortunately, this is not the end of it. After a whole lot of experimentation and poring over the PyObjC source, I finally figured out that in order to get this method to work, you also need to specify metadata for the method that is redundant to this signature. (However, I still haven't puzzled out why.)

This is done using the function objc.registerMetaDataForSelector:

objc.registerMetaDataForSelector(b"SUPERCLASSNAME", 
                                 b"getKey:range:",
        dict(retval=dict(type=objc._C_VOID),
             arguments={ 
                  2+0:  dict(type_modifier=objc._C_OUT,
                             c_array_length_in_arg=2+1),
                  2+1:  dict(type=b'{_NSRange=II}',
                             type64=b'{_NSRange=QQ}')
             }
        )
)

Examples and some details of the use of this function can be found in the file test_metadata_py.py (and nearby test_metadata*.py files) in the PyObjC source.

N.B. that the metadata has to be specified on the superclass of whatever class you are interested in implementing get<Key>:range: for, and also that this function needs to be called sometime before the end of your class definition (but either before or inside the class statement itself both seem to work). I haven't yet puzzled these bits out either.

I based this metadata on the metadata for NSArray getObjects:range: in the Foundation PyObjC.bridgesupport file², and was aided by referring to Apple's BridgeSupport manpage.

With this worked out, it's also worth noting that the easiest way to define the method is (at least, IMO):

@objc.signature('v@:o^@{_NSRange=QQ}')
def get<#Key#>_range_(self, buf, inRange):
    #NSLog(u"get<#Key#>")
    return self.<#Key#>.getObjects_range_(buf, inRange)

I.e., using your array's built-in getObjects:range:.

---

1: On 32-bit Python, the QQ, meaning two unsigned long longs, should become II, meaning two unsigned ints
2: Located (on Snow Leopard) at: /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/PyObjC/Foundation/PyObjC.bridgesupport

这篇关于pyobjc索引访问器方法与范围的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！