init | 易学教程

Python: Inherit the superclass init

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问题 I have a base class with a lot of __init__ arguments: def BaseClass(object): def __init__(self, a, b, c, d, e, f, ...): self._a=a+b self._b=b if b else a ... All the inheriting classes should run __init__ method of the base class. I can write a __init__() method in each of the inheriting classes that would call the superclass __init__ , but that would be a serious code duplication: def A(BaseClass): def __init__(self, a, b, c, d, e, f, ...): super(A, self).__init__(a, b, c, d, e, f, ...) def

In Objective-C why should I check if self = [super init] is not nil?

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问题 I have a general question about writing init methods in Objective-C. I see it everywhere (Apple's code, books, open source code, etc.) that an init method should check if self = [super init] is not nil before continuing with initialisation. The default Apple template for an init method is: - (id) init { self = [super init]; if (self != nil) { // your code here } return self; } Why? I mean when is init ever going to return nil? If I called init on NSObject and got nil back, then something must

Python 3: Calling a class function inside of init

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问题 I have a little question about python 3. I want to create a class, which is using a function from within of that class. Just like: class Plus: def __init__(self, x, y): self.x = x self.y = y self.test() def test(self): return self.x + self.y now I am doing something like a = Plus(5,6) print(a) and python is giving me <__main__.Plus object at 0x000000000295F748> and not 11 as I want it. I know that I can get 11 by a = Plus(5, 6).test() print(a) but that's not what I want. I want to call the

Setting Default Values For NSString Properties

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问题 I am trying to determine the recommended way to set default values for NSString properties. I understand it is not safe to use accessor methods in a class's init and dealloc methods. I often have string constants that I would like to assign default values. What is the recommend way to do this (considering the iVar will be released in the dealloc method)? For example I understand the following is unsafe: @property (nonatomic, copy) NSString *identifier; .... - (id) init { self = [super

what does the numbers mean in /etc/rcX.d?

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问题 In order to run a program automatically on the boot of the Linux system, I have to modify the /etc/rcX.d, to add some link to the script in /etc/init.d, and I have 2 questions: what does the number in the directory's name "/etc/rcNum.d" means? when i add the link file into the rcX.d which directory should add them to? the link file under the directory rcX.d, in their names, there are also some numbers, just like, K90xxx or S90xxx,so what's the number 90 means? is it a priority? then when

Set attribute of all fields in Django ModelForm in init method

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问题 I have a Django ModelForm where I set certain form attributes in the form __init__() method. class MyForm(forms.ModelForm): class Meta: model = MyModel exclude = ['datecreated', 'datemodified'] def __init__(self, *args, **kwargs): super(MyForm, self).__init__(*args, **kwargs) self.fields['field1'].widget.attrs['class'] = 'class1' self.fields['field2'].widget.attrs['class'] = 'class1' self.fields['field3'].widget.attrs['class'] = 'class1' # override Google Chrome field error issues making form

Liferay: get PortletId and Plid from init(PortletConfig) [i.e, no request object, just PortletConfig]

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问题 I would like to get both values, and since init(Portletconfig) is executed when loading the portlet, I don't see any doubt about whether this values should be available. For portletId I tried String portletId = ((PortletConfigImpl) portletConfig).getPortletId(); but it seems I can't. Guess it is because the impl is in another jar not meant to be accessed from portlets By the way, my main goal is to get to pass both params to another non-request context so I can do final PortletPreferences

jMeter - Beanshell bsh.shared hashmap data in init file?

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问题 I have a jMeter project I'm working on which has thrown up all sorts of problems. Mainly due to storing and scoping of variable data throughout the run. I now have things pretty much working and I'm using a Beanshell shared hashmap to store data through the run. I don't need to worry about thread safety due to the way I'm doing it. It works, but it re-initialises itself each time a thread group runs. Despite putting the initialisation step outside all thread groups. So, as I understand it,

Intalio: Difference between 4 ways of adding a form to a process

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问题 I made a form using Intalio's AJAX Widget tool but I was confused once I wanted to add the form to a user's pool. I actually followed this tutorial from Intalio's website. In the 5th slide, they mentioned the ways of adding the form (initProcess, create and complete, notify, escalate), which look like this but no further explanations were given. So, I would like to know the differences between each one of these ways and when should I use one way and not the other. Thanks. 回答1: You use the

【linux】嵌入式 Linux 启动时间优化

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1 简介本章包含的话题有启动时间的测量、分析、人因工程（human factors）、初始化技术和优化技巧等。产品花在启动方面的时间直接影响终端用户对该产品的第一印象。一个消费电子设备不管如何引人注目或者设计得怎么好，设备从关机状态到可交互的使用状态所需的时间对于获得正面的用户体验尤为关键。案例 #1 就是在关机状态从头启动一个设备的例子。启动一个设备涉及到许多步骤和一系列的事件。为了使用前后一致的术语，消费电子 Linux 论坛（CE Linux Forum）的启动时间优化工作组起草了一个术语词汇表，该表包括了相关术语在该领域内通用的定义。该词汇表如下：启动时间相关的词汇表 2 技术/项目主页下面主要介绍与减少 Linux 启动时间有关的各种技术。有一部分描述了 eLinux.org 上可以下载的本地补丁，而其余部分则介绍了在其他地方维护的项目或者补丁。 2.1 测量启动时间 Printk Times – 用于显示每个 printk 的执行时间内核函数跟踪（Ftrace） – 用于报告内核中每个函数的调用时间 Linux 跟踪工具箱（LTT） – 用于报告确切的内核和进程事件的时间数据 Oprofile（译注：最新替代品是 perf） – 通用的 Linux 分析器（Profile） Bootchart – 用于 Linux 启动过程的性能分析和数据展示