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Test if string is a number in Ruby on Rails
...il 1154461.1 (±5.5%) i/s - 5788976 in 5.035311s
require 'benchmark/ips'
int = '220000'
bad_int = '22.to.2'
Benchmark.ips do |x|
x.report('cast') do
Integer(int) rescue false
end
x.report('cast fail') do
Integer(bad_int) rescue false
end
x.report('to_s') do
int.to_i....
屏幕控制使用指导 · App Inventor 2 中文网
...航栏还是屏幕原来的样子。只想隐藏状态栏，用屏幕的「显示状态栏」属性即可。
快速上手
拖一个屏幕控制到屏幕，在设计器属性里勾选保持常亮。运行后只要 App 在前台，屏幕就不会自动熄灭。
案...
Django's SuspiciousOperation Invalid HTTP_HOST header
... a more likely explanation is web crawlers (robots) simply crawling public IP addresses on port 80 - in which case you would want to allow them.
– markmnl
May 16 '14 at 4:12
16
...
write a shell script to ssh to a remote machine and execute commands
...
There are multiple remote linux machines, and I need to write a shell script which will execute the same set of commands in each machine. (Including some sudo operations). How can this be done using shell scripting?
You can do this with ...
Why must a lambda expression be cast when supplied as a plain Delegate parameter
...keRequired code pattern are very helpful.
– Erik Philips
Jan 9 '13 at 1:12
...
Connect Java to a MySQL database
... default 3306.
Download the JDBC driver and put in classpath, extract the ZIP file and put the containing JAR file in the classpath. The vendor-specific JDBC driver is a concrete implementation of the JDBC API (tutorial here).
If you're using an IDE like Eclipse or Netbeans, then you can add it to...
手机串口调试助手：USB OTG 收发文本与十六进制、定时发送（附 .aia 源码）...
...出现在黑色接收区，右上角统计收发字节数。打开「HEX 显示」看原始字节，「暂停接收」时只计数不刷新。
中途验证：Arduino 里 Serial.println("hello")，接收区每次多一行 hello。
发送：输入框写指令，行尾选 \r\n（AT 指令要求）、...
BottomNavigation 拓展：毛玻璃底部导航栏 · App Inventor 2 中文网
...填好图标和文字；
用「选中标签」事件里的 index 决定显示哪一页内容。
when Screen1.Initialize() {
底部导航条1.SetItems(list("home.png", "find.png", "me.png"),
list("首页", "发现", "我的"))
}
when 底部导航条1.ItemSelected(index) ...
虚拟摇杆使用指导 · App Inventor 2 中文网
...化
对照案例检查是否已经调用加载、注册、连接或显示方法；仅拖入组件不会替你执行这些步骤。
结果返回
将成功事件和失败事件都接到标签，记录事件参数；异步操作完成前不读取结果属性。
...
灰度图中找出深色像素并给出坐标 · App Inventor 2 中文网
...
实验一：点哪判哪
手指点在画布上，标签显示这个点的坐标、灰度值，以及是不是深色：
global threshold = 128
when 画布1.Touched(x, y, touchedAnySprite) {
var gray = splitColor(画布1.GetBackgroundPixelColor(x, y))[1]
if (gray < threshold)...