blocks|key|308907|text|您必须使用大括号({})来访问fields，因为fieldnames函数返回字符串的cell+array：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|308908|for+i+=+1:numel(fields)
++teststruct.(fields{i})
end|code-block|syntax|javascript|308909|对access+data+in+your+cell+array使用括号只会返回另一个单元格数组，该数组的显示方式与字符数组不同：|308910|>>+fields(1)++%25+Get+the+first+cell+of+the+cell+array

ans+=+

++++'a'+++++++%25+This+is+how+the+1-element+cell+array+is+displayed

>>+fields{1}++%25+Get+the+contents+of+the+first+cell+of+the+cell+array

ans+=

a+++++++++++++%25+This+is+how+the+single+character+is+displayed|308911|entityMap|0|LINK|mutability|MUTABLE|url|https://www.mathworks.com/help/matlab/ref/fieldnames.html|1|https://www.mathworks.com/help/matlab/cell-arrays.html|2|https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html^0|9|2|F|6|O|A|O|A|0|16|A|1|0|0|1|U|2|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]|$9|1A|A|1B|1|1C]]|E|$]]|$1|F|3|G|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1E|8|@]|D|@$9|1F|A|1G|1|1H]]|E|$]]|$1|M|3|N|5|H|7|1I|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]|Y|$5|R|S|T|E|$U|Z]]]]

You have to use curly braces (<code>{}</code>) to access <code>fields</code>, since the <a href="https://www.mathworks.com/help/matlab/ref/fieldnames.html" rel="noreferrer"><code>fieldnames</code></a> function returns a <a href="https://www.mathworks.com/help/matlab/cell-arrays.html" rel="noreferrer">cell array</a> of strings:

<pre><code>for i = 1:numel(fields)
 teststruct.(fields{i})
end
</code></pre>

Using parentheses to <a href="https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html" rel="noreferrer">access data in your cell array</a> will just return another cell array, which is displayed differently from a character array:

<pre><code>&gt;&gt; fields(1) % Get the first cell of the cell array

ans = 

 'a' % This is how the 1-element cell array is displayed

&gt;&gt; fields{1} % Get the contents of the first cell of the cell array

ans =

a % This is how the single character is displayed
</code></pre>

blocks|key|3258779|text|你的fns是一个cellstr数组。您需要使用{}而不是()对其进行索引，才能将单个字符串作为char输出。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3258780|fns{i}
teststruct.(fns{i})|code-block|syntax|javascript|3258781|使用()对其进行索引将返回一个1长的cellstr数组，该数组与".(name)“动态字段引用所需的char数组的格式不同。格式化，特别是在显示输出中，可能会令人困惑。要查看不同之处，请尝试这个。|3258782|name_as_char+=+'a'
name_as_cellstr+=+{'a'}|3258783|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Your fns is a cellstr array. You need to index in to it with {} instead of () to get the single string out as char.

<pre><code>fns{i}
teststruct.(fns{i})
</code></pre>

Indexing in to it with () returns a 1-long cellstr array, which isn't the same format as the char array that the ".(name)" dynamic field reference wants. The formatting, especially in the display output, can be confusing. To see the difference, try this.

<pre><code>name_as_char = 'a'
name_as_cellstr = {'a'}
</code></pre>

blocks|key|307974|text|由于fields或fns是单元格数组，您必须使用花括号{}进行索引，以便访问单元格的内容，即字符串。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|307975|请注意，您也可以直接在fields上循环，而不是在数字上循环，这利用了一个整洁的Matlab特性，它允许您循环遍历任何数组。iteration变量采用数组的每一列的值。|307976|teststruct+=+struct('a',3,'b',5,'c',9)

fields+=+fieldnames(teststruct)

for+fn=fields'
++fn
++%25#+since+fn+is+a+1-by-1+cell+array,+you+still+need+to+index+into+it,+unfortunately
++teststruct.(fn{1})
end|code-block|syntax|javascript|307977|entityMap^0|2|6|9|3|R|2|0|B|6|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|N|$]]

Since <code>fields</code> or <code>fns</code> are cell arrays, you have to index with curly brackets <code>{}</code> in order to access the contents of the cell, i.e. the string. 

Note that instead of looping over a number, you can also loop over <code>fields</code> directly, making use of a neat Matlab features that lets you loop through any array. The iteration variable takes on the value of each column of the array.

<pre><code>teststruct = struct('a',3,'b',5,'c',9)

fields = fieldnames(teststruct)

for fn=fields'
 fn
 %# since fn is a 1-by-1 cell array, you still need to index into it, unfortunately
 teststruct.(fn{1})
end
</code></pre>

blocks|key|3258800|text|您可以使用http://www.mathworks.com/matlabcentral/fileexchange/48729-for-each中的每个工具箱。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3258801|>>+signal
signal+=+
sin:+{{1x1x25+cell}++{1x1x25+cell}}
cos:+{{1x1x25+cell}++{1x1x25+cell}}

>>+each(fieldnames(signal))
ans+=+
CellIterator+with+properties:

NumberOfIterations:+2.0000e%2B000|code-block|syntax|javascript|3258802|用法：|3258803|for+bridge+=+each(fieldnames(signal))
+++signal.(bridge)+=+rand(10);
end|3258804|我非常喜欢它。当然，功劳要归功于Jeremy+Hughes，他开发了这个工具箱。|3258805|entityMap|0|LINK|mutability|MUTABLE|url|http://www.mathworks.com/matlabcentral/fileexchange/48729-for-each^0|5|1U|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

You can use the for each toolbox from <a href="http://www.mathworks.com/matlabcentral/fileexchange/48729-for-each" rel="nofollow">http://www.mathworks.com/matlabcentral/fileexchange/48729-for-each</a>. 



<pre class="lang-matlab prettyprint-override"><code>&gt;&gt; signal
signal = 
sin: {{1x1x25 cell} {1x1x25 cell}}
cos: {{1x1x25 cell} {1x1x25 cell}}

&gt;&gt; each(fieldnames(signal))
ans = 
CellIterator with properties:

NumberOfIterations: 2.0000e+000
</code></pre>

Usage:

<pre class="lang-matlab prettyprint-override"><code>for bridge = each(fieldnames(signal))
 signal.(bridge) = rand(10);
end
</code></pre>

I like it very much. Credit of course go to Jeremy Hughes who developed the toolbox.

My question is easily summarized as: "Why does the following not work?"

<pre><code>teststruct = struct('a',3,'b',5,'c',9)

fields = fieldnames(teststruct)

for i=1:numel(fields)
 fields(i)
 teststruct.(fields(i))
end
</code></pre>

output:

<pre><code>ans = 'a'

??? Argument to dynamic structure reference must evaluate to a valid field name.
</code></pre>

Especially since <code>teststruct.('a')</code> does work. And <code>fields(i)</code> prints out <code>ans = 'a'</code>.

I can't get my head around it.

Iterating through struct fieldnames in MATLAB

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我的问题很容易概括为：“为什么下面的问题不起作用？”teststruct = struct('a',3,'b',5,'c',9)fields = fieldnames(teststruct)for i=1:numel(fields)  fields(i)  teststruct.(fields(i))end输出：ans...

问在MATLAB中遍历struct字段名
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