IT 技术分享 (Page 27)

diesel cannot infer type of the type parameter `U` declared on the method

Use load:: to specify the type. fn count_packages() -> i64 { let conn = &mut establish_connection("mysql://root:cpchain@127.0.0.1:3306/cpchain"); let found = packages.filter(name.eq("name")).filter(

Why Pepe coin is so welcome?

There are a few reasons why the Pepe coin is so welcome. * The popularity of Pepe the Frog meme. Pepe the Frog is a popular meme that has been around for many years.

Actix-web return response early from middleware

The function of this middleware is to check the client's IP, if not in the white list, return a Forbidden response early. use std::{future::{ready, Ready}, collections::HashSet}; use actix_web::{dev:

rust

Actix-web 在中间件中返回 response

中间件功能为“检查 client IP，如果不在 allow 范围内，则提前返回 forbidden response”，代码如下： use std::{future::{ready, Ready}, collections::HashSet}; use actix_web::{dev::{Transform, Service, ServiceRequest, ServiceResponse, forward_ready}, Error, HttpResponse}; use futures_util:

How to Develop a React Native Project

React Native is a framework that allows you to build native mobile apps using JavaScript. This means that you can use the same code to build apps for both Android and iOS. React

CPChain and Web3: The Future of the Internet

The internet has changed the way we live, work, and communicate. It has given us access to information and entertainment that was once unimaginable. But the internet is also centralized, meaning that it

Best forums to follow of Web3

* For general discussion: * Reddit * Quora * Hacker News * Slashdot * Digg * For specific topics: * Stack Overflow * GitHub Discussions * DigitalOcean Community * AWS Forums * Azure Community * For professional development: * LinkedIn Learning * Pluralsight * Udemy * Coursera * EdX You can

Best Twitter accounts to follow for web3 news, updates, and analysis

* Andreessen Horowitz (@a16z): A16z is a venture capital firm that has invested in some of the biggest web3 companies, including Coinbase, OpenSea, and Dapper Labs. * Coinbase (@coinbase): Coinbase is the largest cryptocurrency exchange

使用 pnpm 搭建 react typescript 项目

pnpm create react-app wudom-app --template typescript

golang

Golang 字符串是否存在于数组中

基本原理，使用 sort 库，先对数组排序，再二分搜索进行确认。 func assert(actual, expect bool, t *testing.T) { if actual != expect { t.Fatalf("Expect %v, but got %v", expect, actual) } } func TestSearchInArray(t *testing.T) { assert(In(

技术

国内 Ubuntu 20.04 安装kubeadm

命令如下： sudo apt-get update && apt-get install -y apt-transport-https ca-certificates curl # 更换镜像 curl https://mirrors.aliyun.com/kubernetes/apt/doc/apt-key.gpg | sudo apt-key add - echo "deb https://mirrors.aliyun.com/kubernetes/apt/

python

Python 3.9 报错 AttributeError: 'HTMLParser' object has no attribute 'unescape'

原因是 HTMLParser.unescape 在 3.9 中被废弃了。解决办法，可以降下版本，降到 3.8，或者升级 setuptools： pip3 install --upgrade setuptools 如果是运行pip install -r requirements.txt，升级后有可能还是不行，因为依赖包里可能有某个包对 setuptools 有版本要求，所以在运行中，又重新降级了，对这种情况，建议直接将 Python 降级到

javascript

Javascript 过滤数组

使用 filter 可从数组中快速找出符合条件的元素组成新元素。示例如下： [1,2,3].filter(i => i > 2) > [3] 其中， i => i>2 为简化的 Lambda 表达式，等价于： i => { return i > 2 }

Docker

Docker 从容器中复制文件或文件夹

命令如下： docker cp <容器ID>:/file/path/within/container /host/path/target

latex

Latex 希腊字母表

Latex 希腊字母表：希腊字母小写、大写LaTeX语法α A\alpha Aβ B\beta Bγ Γ\gamma \Gammaδ Δ\delta \ Deltaϵ ε E \epsilon \varepsilon Eζ Z\zeta Zη H\eta Hθ ϑ Θ\theta \vartheta \Thetaιι I\

latext

Latex 属于集合和不属于集合

其实很简单，Latex 很多符号都是语义化的。就是 in 和 not in。 a \in A b \notin B 展示如下： \[ a \in A, b \notin B \]

latex

Latex 大括号语法

Latex 大括号语法如下： \left\{ \begin{aligned} 1 \\ 2 \\ 3 \\ 4 \\ 5 \end{aligned} \right. 显示如下： \[ \left\{ \begin{aligned} 1 \\ 2 \\ 3 \\ 4 \\ 5 \end{aligned} \right. \]

latex

Latex 大于等于号和小于等于号

大于等于号： \geq \[ \geq \] 小于等于号： \leq \[ \leq \]

golang

Golang SHA256 及将哈希值转化为字符串

Golang 做 SHA256 哈希，以及将哈希值转化为字符串，如下： import ( "crypto/sha256" "fmt" "testing" ) func TestSHA256(t *testing.T) { b := sha256.Sum256([]byte("Hello world")) // 转化为字符串 s := fmt.Sprintf("%x", b) fmt.Println(s) }

terraform

在 ubuntu 上安装 Terraform

在 ubuntu 上安装 Terrform，执行以下命令： curl -fsSL https://apt.releases.hashicorp.com/gpg | sudo apt-key add - sudo apt-add-repository "deb [arch=$(dpkg --print-architecture)] https://apt.releases.hashicorp.com $(lsb_release -cs) main" sudo

Docker

查看及清理 docker 容器日志

docker 容器日志太大，导致磁盘占用过高，需定时清理（也可提前限制容器日志大小）。一般情况下，容器日志位于 /var/lib/docker/containers//-json.log。可编写脚本如下 vim check-docker-logs： #!/bin/sh echo "======== start clean========" logs=$(find /var/lib/docker/containers/ -name *-json.log) for log in

golang

Golang Hex 字符串转 big.Int

如下，先创建一个 big.Int，再设置其值为16进制的字符串： package main import ( "fmt" "math/big" ) func main() { s := "a" i := new(big.Int) i.SetString(s, 16) fmt.Println(i) // 10 } 请注意，十六进制字符串不要以 0x 开头。

spring-boot

Spring Boot 生成图片验证码

基本原理就是用Java画张指定大小的图片，在图片上随机摆上若干个数字或字母，数字或字母要有一定的倾斜和位移，要变一下字体和颜色，再画几条干扰线，然后就可以返回给客户端了。创建文件 CaptchaUtil.java，代码如下： // Write your package import javax.imageio.ImageIO; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import

MySQL

MySQL查看表的数量

SQL 语句如下，指定好表名即可： SELECT COUNT(*) TABLES, table_schema FROM information_schema.TABLES WHERE table_schema = '' GROUP BY table_schema;

kubernetes

国内搭建minikube实验环境

阿里云维护了一个国内版本的minikube库，并提供了相应的安装教程。请参考： https://developer.aliyun.com/article/221687