使用 PyObjC 访问 iPhone 加速计

发布于 2024-10-21 15:20:43 字数 732 浏览 7 评论 0 原文

我想通过 PyObjC 访问 iPhone 的加速计。这是我的代码：

@objc.signature("v@:@@")
def accelerometer_didAccelerate_(self, accelerometer, acceleration):
    msgBox = UIAlertView.alloc().initWithTitle_message_delegate_cancelButtonTitle_otherButtonTitles_("Acceleration", str(acceleration.x), self, "OK", None)
    msgBox.show()
    msgBox.release()

@objc.signature("v@:@")
def applicationDidFinishLaunching_(self, unused):
    self.accelerometer = UIAccelerometer.sharedAccelerometer()
    self.accelerometer.setUpdateInterval_(1)
    self.accelerometer.setDelegate_(self)
    #...

问题是 str(accelleration.x) 返回 ">"。我能做些什么？

原文

I want to access the Accelerometer of my iPhone through PyObjC.
Here is my Code:

@objc.signature("v@:@@")
def accelerometer_didAccelerate_(self, accelerometer, acceleration):
    msgBox = UIAlertView.alloc().initWithTitle_message_delegate_cancelButtonTitle_otherButtonTitles_("Acceleration", str(acceleration.x), self, "OK", None)
    msgBox.show()
    msgBox.release()

@objc.signature("v@:@")
def applicationDidFinishLaunching_(self, unused):
    self.accelerometer = UIAccelerometer.sharedAccelerometer()
    self.accelerometer.setUpdateInterval_(1)
    self.accelerometer.setDelegate_(self)
    #...

The problem is str(accelleration.x) returns "<native-selector x of <UIAcceleration: 0x.....>>". What can I do?

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入画浅相思 2024-10-28 15:20:43

UIAcceleration 的 x 值在 Objective-C 中定义为属性，并在 Python 中访问 acceleration.x 为您提供方法名为“x”，而不是您可能期望的名为“x”的属性 (ivar)。你需要说：

acceleration._.x

它使用 PyObjC 的“神奇”访问器机制来获取你想要的属性。

原因是：

Python 类命名空间的工作方式是，不能有同名的方法和属性。这与 Objective-C 形成鲜明对比，在 Objective-C 中，getter 方法通常与其访问的属性具有相同的名称。

这种差异可能会导致与 Objective-C 2.0 的属性功能产生一些混淆，特别是因为两种语言之间的语法看起来相同。在 Objective-C 中，您可以编写：

NSLog(@"foo's bar: %f", foo.bar);
foo.bar = 10.0;

它会自动使用正确的 setter 或 getter 方法（-bar 和 -setBar:）。由于 Python 的类命名空间规则，PyObjC 无法完全执行 Objective-C 代码将执行的操作，并且必须仅选择一个事物（方法或属性）来由名称 foo.bar 表示。 >;它选择的是方法。

A UIAcceleration's x-value is defined in Objective-C as a property, and accessing acceleration.x in Python gives you the method named 'x', not the attribute (ivar) named 'x' as you might expect. You need to say:

acceleration._.x

which uses PyObjC's "magic" accessor mechanism to get the attribute you want.

The reasons for this:

The way Python's class namespaces work, you can't have a method and an attribute with the same name. This is in contrast to Objective-C where a getter method often has the same name as the attribute it accesses.

This difference can cause a little confusion with Objective-C 2.0's properties feature, especially since the syntax looks identical between the two languages. In Objective-C, you write:

NSLog(@"foo's bar: %f", foo.bar);
foo.bar = 10.0;

Which automatically uses the proper setter or getter methods (-bar and -setBar:). PyObjC, because of Python's class namespace rule, can't do exactly what the Objective-C code would do, and has to pick just one thing (method or attribute) to be represented by the name foo.bar; the thing it chooses is the method.