Using the optional “+” sign together with mapped type modifiers, we can create more explicit and readable type declarations. We can also use the “-” (minus) sign to remove optional declarations from properties. For example, we have an interface: inte…

条款5 相对显式类型声明,更倾向使用auto 基础知识 auto能大大方便变量的定义,可以表示仅由编译器知道的类型. template<typename It> void dwim(It b, It e) { while(b != e) { //typename std::iterator_traits<It>::value_type currValue = *b; // old type auto currValue = *b; // new type } } auto可以用来定…

You can create an easy to chain API using TypeScript classes. Learn about the thisreturn type annotation and how it plays with function chaining and class inheritance. class Adder { ; add(num: number): Adder { this.acc += num; return this; // enable…

go version go1.11 windows/amd64 本文为阅读Go语言中文官网的规则说明书(https://golang.google.cn/ref/spec)而做的笔记,完整的介绍Go语言的 类型声明(Type declarations). 类型声明 即 绑定一个标识符(新类型名称) 到 一个类型. 有两种形式:类型别名声明(alias declarations).新类型定义(type definitions). 类型别名声明 很简单:在类型别名和类型之间使用等号(=).官文示例:…

When working with conditionals types, within the “extends” expression, we can use the “infer” keyword to either get the type of the elements of an array, or even to get the return type of a function. We can use this to build a “FnReturnType” type, th…

Sometimes we want our function arguments to be able to accept more than 1 type; e.g. a string or an array. This lesson will show us how to assign more than 1 type to a variable with Typescript union types and type aliases. type types = string | boole…

This lesson introduces the --strictNullChecks compiler option and explains how non-nullable types differ from nullable types. It also illustrates how you can write safer code by being explicit about null and undefined in the type system. First of all…

封装目的:屏蔽底层实现,提供统一接口,并支持Gson自动转化 最初封装: //请求方法 interface RequestListener { interface PostListener { @POST fun <T>call(@Url url: String, @Body t:Any) : Call<T> } } //封装请求 class NetUtils private constructor(retrofit: Retrofit){ private val mRetrofi…

今天做springbook项目前端输入日期传到数据库保存报了一下错误 Whitelabel Error Page This application has no explicit mapping for /error, so you are seeing this as a fallback. Sun Feb 09 16:31:32 CST 2020 There was an unexpected error (type=Bad Request, status=400). Validation…

刚刚有在程序中,传递一个空值至MS SQL Server数据库,这个值的数据类型为DATETIME执行时,它却发生了如标题提示的异常:The conversion of a varchar data type to a datetime data type resulted in an out-of-range value. 跟踪一下,当遇上一个空值时,它并没有真正是给一个空值给数据库,而是Datetime的最小值"1/1/0001 12:00:00 AM" 在两个文本框都是空值时,跟…