One aspect of control flow based type analysis is that the TypeScript compiler narrows the type of a variable within a type guard. This lesson explores how you can define functions and type predicates to create your own type guards similar to the Arr…

TypeScript 3.7 RC & Assertion Functions assertion functions, assert https://devblogs.microsoft.com/typescript/announcing-typescript-3-7-rc/#assertion-functions function yell(str) { assert(typeof str === "string"); return str.toUppercase(); /…

#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)宏的运行机理:1. ( (TYPE *)0 ) 将零转型为TYPE类型指针; 2. ((TYPE *)0)->MEMBER 访问结构中的数据成员; 3. &( ( (TYPE *)0 )->MEMBER )取出数据成员的地址; 4.(size_t)(&(((TYPE*)0)->MEMBER))结果转换类型.巧妙之处在于将0转 换成(TY…

引用:https://jamilgeor.com/binding-a-xamarin-forms-webview-to-reactiveui-view-model-using-custom-type-converters/ Introduction In this article, we will expand on our demo app, by displaying article content inside of a WebView after the user is navigate…

https://www.jianshu.com/p/47054d92db2a 自定义类型转换器(Custom Type Converters) 有时需要完全控制一种类型到另一种类型的转换.这一般发生在两种类型不同,已经存在转换函数,并且希望从弱类型转变为强类型,如源类型的字符串到目标类型Int32. 例如,假设我们的源类型为: public class Source { public string Value1 { get; set; } public string Value2 { get;…

#include <iostream> #define IOFFSETOF(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) using namespace std; int main(){ struct Demo{ char sex; int id; }; cout << "IOFFSETOF(Demo, sex): " << IOFFSETOF(Demo, sex) << end…

type DigitValidator = (char) => boolean; -]{}/.test(char); export const digitValidators: {[key: string]: DigitValidator} = { ': numericValidator }; We can use 'type' keyword to define a function type. 'digitValidators', is a mapping object, return a…

TypeScript 2.0 introduced a new primitive type called never, the type of values that never occur. It helps model the completion behavior of functions more accurately and can also be used for exhaustiveness checking. never type means that 'That part o…

To avoid using "any" type is a best pratice. The reason for that is it disable the power of typescirpt to helping check you during the compile time. For example: currency(num: number){ cosnole.log(num.toFixed()); } In our currency function, it s…

ypeScript 2.2 introduced the object, a type that represents any non-primitive type. It can be used to more accurately type methods such as Object.create. Don't confuse it with the Object type or {}, the empty object type, though! So one thing we need…