将字段添加到空结构 [英] Adding a field to an empty struct

问题描述

假设我有一个大小为0x1的结构S，其中有字段a和b，向其中添加字段c的最优雅方法是什么?

Assuming I have a struct S of size 0x1 with the fields a and b, what is the most elegant way to add a field c to it?

通常我可以这样:

S = struct('a',0,'b',0); %1x1 struct with fields a,b
S.c = 0

但是，如果我收到一个空结构，它将不再起作用:

However, if I receive an empty struct this does not work anymore:

S = struct('a',0,'b',0);
S(1) = []; % 0x1 struct with fields a,b
S.c = 0;
% A dot name structure assignment is illegal when the structure is empty.  
% Use a subscript on the structure.

我已经想到了两种方法来解决此问题，但是这两种方法都很丑陋，感觉像是变通方法，而不是解决方案. (请注意，也应正确处理非空结构的可能性.)

I have thought of two ways to deal with this, but both are quite ugly and feel like workarounds rather than solutions. (Note the possibility of a non-empty struct should also be dealt with properly).

1. 向结构中添加一些内容以确保其不为空，添加字段，然后再次使结构为空
2. 使用所需的字段名初始化新结构，将原始结构中的数据填充其中，并覆盖原始结构

我意识到我关心空结构可能很奇怪，但是不幸的是，如果不存在该字段名，那么部分由我管理的代码将崩溃.我查看了help struct，help subsasgn，还搜索了给定的错误消息，但到目前为止，我还没有发现任何提示.因此，非常感谢您的帮助！

I realize that it may be odd that I care about empty structs, but unfortunately part of the code that is not managed by me will crash if the fieldname does not exist. I have looked at help struct, help subsasgn and also searched for the given error message but so far I have not yet found any hints. Help is therefore much appreciated!

推荐答案

您可以使用

You can use deal to solve this problem:

S = struct('a',0,'b',0);
S(1) = [];

[S(:).c] = deal(0);

这导致

S = 

1x0 struct array with fields:
    a
    b
    c 

这也适用于非空结构:

S = struct('a',0,'b',0);

[S(:).c] = deal(0);

结果

S = 

    a: 0
    b: 0
    c: 0

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