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可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Is there a way to run a piece of JavaScript code only ONCE , without using boolean flag variables to remember whether it has already been ran or not? Specifically not something like: var alreadyRan = false; function runOnce() { if (alreadyRan) { return; } alreadyRan = true; /* do stuff here */ } I'm going to have a lot of these types of functions and keeping all booleans would be messy... 回答1: An alternative way that overwrites a function when executed so it will be executed only once. function useThisFunctionOnce(){ // overwrite this

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm using react-native-fetch-blob module to handle image upload, I currently pass only the image data to the POST method, but is there any way to extend this by passing a custom data object? In the server side, it reads the image data base64, I crop & resize the image and return the image URL to my app. With that image URL i have to do another HTTP POST to the server with the form data + the image URL I just got. I was wondering if there's any chance to send all the data (including image data) at once instead of doing 2 separate POST

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Let's say I have a C structure defined as struct data { /* some memebers */ int flag_a:1; int flag_b:1; int flag_c:1; /* some other members */ } Is there a way to take advantage of the bitfields being represented as a single int in memory and write the condition s.flag_a | s.flag_b | s.flag_c as a simpler expression such as s.flags ? Or would a smart compiler such as GCC be able to actually deduce it? Edit: To make myself absolutely clear: I'm looking for a portable way to test for all the flags being set without explicitly testing each of

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am getting the following errors after an upgrade. I cannot figure what is wrong with it. It should work as far as I can see. $ make 2>&1 | head g++ -o prog -ansi -O2 -Wall -I/usr/include/boost -L/usr/lib -lboost_program_options -lboost_thread -lstdc++ ./YYY.o ./main.o ./myClass.o ./YYY.o: In function `void boost::call_once<void (*)()>(boost::once_flag&, void (*)())': YYY.cc:(.text._ZN5boost9call_onceIPFvvEEEvRNS_9once_flagET_[void boost::call_once<void (*)()>(boost::once_flag&, void (*)())]+0x14): undefined reference to `boost::detail::get

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: My Python version is 2.6. I would like execute the setUp method only once since I'm doing there things which are needed for every test. My idea was to create a boolean var which will be set to 'true' after the first execution. The output: False True --- Test 1 --- False True --- Test 2 --- why is this not working? Did I missed something? 回答1: You can use setUpClass to define methods that only run once per testsuite. 回答2: Daniel's answer is correct, but here is an example to avoid some common mistakes I found, such as not calling super() in

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I have an activity that i only want to run when the application is ran for the first time. And never again. It is a facebook login activity. I only want to launch it once when the app is initially opened for the first time. How do i go about doing this? 回答1: What I've generally done is add a check for a specific shared preference in the Main Activity : if that shared preference is missing then launch the single-run Activity, otherwise continue with the main activity . When you launch the single run Activity create the shared

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: http://hackage.haskell.org/package/free in Control.Monad.Free.Free allows one to get access to the "free monad" for any given Functor . It does not, however, have a MonadFix instance. Is this because such an instance cannot be written, or was it just left out? If such an instance cannot be written, why not? 回答1: Consider the description of what mfix does: The fixed point of a monadic computation. mfix f executes the action f only once, with the eventual output fed back as the input. The word "executes", in the context of Free , means

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am using the new concurrent.futures module (which also has a Python 2 backport) to do some simple multithreaded I/O. I am having trouble understanding how to cleanly kill tasks started using this module. Check out the following Python 2/3 script, which reproduces the behavior I'm seeing: #!/usr/bin/env python from __future__ import print_function import concurrent.futures import time def control_c_this(): with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor: future1 = executor.submit(wait_a_bit, name="Jack") future2 =

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have used the code from here in my app, when I click on 'Cancel' option ,the app just minimizes ,when I long press and hold Home button and select the app.It shows the same screen not the splashscreen or the usual way the app starts - So I am assuming it just takes me to home screen. I am looking for a way I can close the main activity completely. I have tried the following methods and it crashed every time: finish(); mainactivity.class.finish(); opening an intent which has systemexit() setresult() in the another activity. 回答1: Not

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: i need to require_once this files main.class.php and functions.php and config.php to admin/test.php . how to php find require real path?! NOTE: main.class.php in class folder , functions.php in includes folder and config.php in root directory and test.php in admin folder . File Directory: root /admin/ ->test.php /class/ ->main.class.php /includes/ ->functions.php /templates config.php phpinfo.php 回答1: I would add your root folder to the include path and work from there. From admin/test.php set_include_path(implode(PATH_SEPARATOR, array(