ref

问题 I thought I understood limitations of ref returns as well as escaping scopes. But now I found a case and I don't get why is it illegal. It seems that ref return cannot be used if the value to return comes from a nested method with any ref/out arguments. public static ref T RefReturn<T>() { ref T result = ref GetResult<T>(normalParam: default); // compiles // ref T result = ref GetResult<T>(out bool outParam); // CS8157 at the return statement // ref T result = ref GetResult<T>(boxedParam: new

问题 I have an ASP.NET MVC 4 Web API app using EntityFramework for ORM. In the JSON I return, there are some cases where the same child node is present for multiple parent nodes. In these cases, the first occurrence of the child node is fully visible with all it's members. Any subsequent occurrence shows up as a $ref to the first occurrence. I'd like instead to see the full object everytime it shows up in the JSON returned. For example, instead of seeing: [{ "$id": "1", "userId": 1, "Badge": { "

问题 I have an ASP.NET MVC 4 Web API app using EntityFramework for ORM. In the JSON I return, there are some cases where the same child node is present for multiple parent nodes. In these cases, the first occurrence of the child node is fully visible with all it's members. Any subsequent occurrence shows up as a $ref to the first occurrence. I'd like instead to see the full object everytime it shows up in the JSON returned. For example, instead of seeing: [{ "$id": "1", "userId": 1, "Badge": { "

问题 I am building a carousel right now, in React. To scroll to the individual slides I am using document.querySelector like so : useEffect(() => { document.querySelector(`#slide-${activeSlide}`).scrollIntoView({ behavior: 'smooth', block: 'nearest', inline: 'nearest' }); }, [activeSlide]); Is this bad practice? After all, I am accessing the DOM directly here? What would be the React way of doing this? edit: full return method return ( <> <button onClick={() => setActiveSlide(moveLeft)}>PREV<

问题 I am building a carousel right now, in React. To scroll to the individual slides I am using document.querySelector like so : useEffect(() => { document.querySelector(`#slide-${activeSlide}`).scrollIntoView({ behavior: 'smooth', block: 'nearest', inline: 'nearest' }); }, [activeSlide]); Is this bad practice? After all, I am accessing the DOM directly here? What would be the React way of doing this? edit: full return method return ( <> <button onClick={() => setActiveSlide(moveLeft)}>PREV<

问题 I have a ref : const editItem = ref<object | null>(null) Here's an example value for it: { id: 1, title: 'Harry Potter', author: 'J.K. Rowling', created: '30-08-2000', } If I run console.log(editItem.value) , I see this object: But when I try to read the value's author with console.log(editItem.value.author) , then I see this error: Object is possibly 'null'. 回答1: Since the type of the ref is object | null , it could be null when you access it, leading to a runtime exception. The error

问题 I have some issues when im trying to reference inputs as arrays in React with Redux. The code below maps one Panel per article in the array. var articles = this.props.item.array.articles.map((article, index) => { return <Panel key={index} header={'Article ' + index}> <Input type='select' ref='id' label='Article' defaultValue={article.id} > {articles} </Input> </Panel> }) I'm trying to construct the refs so that they're in an array format, which does not seem to be possible at the moment.

问题 With the new readonly instance member features in C# 8, I try to minify unnecessary copying of struct instances in my code. I do have some foreach iterations over arrays of structs, and according to this answer, it means that every element is copied when iterating over the array. I thought I can simply modify my code now to prevent the copying, like so: // Example struct, real structs may be even bigger than 32 bytes. struct Color { public int R; public int G; public int B; public int A; }

问题 To my knowledge this in a extension method is passed as a ref variable. I can verify this by doing public static void Method<T>(this List<T> list) { list.Add(default(T)); } List<int> ints = new List<int>(new int[] { 1, 2, 3, 4, 5 }); ints.Method(); My List<int> ints is now 1, 2, 3, 4, 5, 0 . However when I do public static void Method<T>(this List<T> list, Func<T, bool> predicate) { list = list.Where(predicate).ToList(); } List<int> ints = new List<int>(new int[] { 1, 2, 3, 4, 5 }); ints

问题 To my knowledge this in a extension method is passed as a ref variable. I can verify this by doing public static void Method<T>(this List<T> list) { list.Add(default(T)); } List<int> ints = new List<int>(new int[] { 1, 2, 3, 4, 5 }); ints.Method(); My List<int> ints is now 1, 2, 3, 4, 5, 0 . However when I do public static void Method<T>(this List<T> list, Func<T, bool> predicate) { list = list.Where(predicate).ToList(); } List<int> ints = new List<int>(new int[] { 1, 2, 3, 4, 5 }); ints