Convert Struct to Readable JSON(Pretty Print)

Every struct I pass to jsonecode gets converted to a 1 by N char array with no newline chacters. Therefore, when I export the json as to a text file I only have one line. The file is not easly readble because I have to scroll the JSON text horizontaly. How can I make jsonencode's output easily readable(pretty print)?

I get this.

{ "firstName": "John", "lastName": "Smith", "age": 25, "address": { "streetAddress": "3 Apple Hill Dr", "city": "Natick", "state": "MA", "postalCode": "01760" }, "phoneNumber": [ { "type": "home", "number": "123 456 7890" }, { "type": "cell", "number": "098 765 4321" } ] }

I want something like this.

{

"firstName": "John",

"lastName": "Smith",

"age": 25,

"address":

{

"streetAddress": "3 Apple Hill Dr",

"city": "Natick",

"state": "MA",

"postalCode": "01760"

},

"phoneNumber":

[

{

"type": "home",

"number": "123 456 7890"

},

{

"type": "cell",

"number": "098 765 4321"

}

]

}

[Jan Zalewski]

I have the same problem

according to documentation jsonencode has "PrettyPrint" value that shoudl do just that, unfortunately this doesn't seem to be working on newer version of matlab

[Martin]

I would like to see the PrettyPrint option supported as well. Is it introduced in release 2021a then?

[Sean Bone]

@Martin yes, it was introduced in R2021a.

[Davide Serina]

ciao, come si fa ad ottenere una struttura come quella che hai scritto partendo da una struttura su matlab?! cioè non riesco a fare gli annidamenti. bisogna usare un ciclo for???

[Sean Bone]

Ciao @Davide Serina, la tua domanda si riferisce a come creare una struttura annidata in MATLAB o a come convertire una struttura annidata in JSON? Oppure ancora a come convertire una struttura MATLAB in JSON con le indentature per rappresentare gli annidamenti?

Answer 1

[Sean Bone]

In more recent Matlab versions, you can do the following:

jsonencode(data, "PrettyPrint", true);

Note that this option was only introduced in Matlab R2021a, despite the documentation for jsonencode not mentioning this explicitly.

[ILoveMATLAB]

I guess I will accept this anwser; although, I was using an older version of matlab when I wrote this question.

Answer 2

[Robin Larsson Nordström]

For the provided example the default pretty print output will be fine:

txt=jsonencode(data, "PrettyPrint", true);

However if the input data struct contains fields with vectors or matrices the jsonencode PrettyPrint in Matlab 2023b adds a newline for each element, making the encoded text hard to read even when the number of elements are not that many.

Post-processing the output with a few regexprep lines to remove white-spaces inside vectors and matrices have worked well for me. Example below with the struct from the Matlab help on jsonencode PrettyPrint example with the addition of an extra field Q storing a 4 X 4 matrix:

s=[];
s.Width = 800;
s.Height = 600;
s.Title = 'View from the 15th Floor';
s.Animated = false;
s.IDs = [116, 943, 234, 38793];
s.Q = round(randn(4),3);
txt=jsonencode(s,PrettyPrint=true)

txt = 
    '{
       "Width": 800,
       "Height": 600,
       "Title": "View from the 15th Floor",
       "Animated": false,
       "IDs": [
         116,
         943,
         234,
         38793
       ],
       "Q": [
         [
           0.104,
           -1.164,
           -2.504,
           1.22
         ],
         [
           -0.277,
           -1.496,
           0.394,
           2.864
         ],
         [
           0.418,
           0.155,
           -0.266,
           0.515
         ],
         [
           1.536,
           0.02,
           0.071,
           1.06
         ]
       ]
     }'

% remove white-spaces inside vectors and matrices
txt = regexprep(txt,',\s+(?=\d)',','); % , white-spaces digit
txt = regexprep(txt,',\s+(?=-)',','); % , white-spaces minussign
txt = regexprep(txt,'[\s+(?=\d)','['); % [ white-spaces digit
txt = regexprep(txt,'[\s+(?=-)','['); % [ white-spaces minussign
txt = regexprep(txt,'(?<=\d)\s+]',']'); % digit white-spaces ]
txt

txt = 
    '{
       "Width": 800,
       "Height": 600,
       "Title": "View from the 15th Floor",
       "Animated": false,
       "IDs": [116,943,234,38793],
       "Q": [
         [0.104,-1.164,-2.504,1.22],
         [-0.277,-1.496,0.394,2.864],
         [0.418,0.155,-0.266,0.515],
         [1.536,0.02,0.071,1.06]
       ]
     }'

[John Wittig]

very slick and helpful!

Answer 3

[Gaurav Garg]

Hi,

You can find a function which can help you resolve the problem you are facing in this file.

[Laurel Keyes]

This file is helpful but not if you have nested structures. I use a quick and dirty method, where you just string-replace the commas or brackets like so:

% assuming your structure is saved to val:
str = jsonencode(val);
% add a return character after all commas:
new_string = strrep(str, ',', ',\n');
% add a return character after curly brackets:
new_string = strrep(new_string, '{', '{\n')
% etc...
% Write the string to file
fid = fopen("filename.json",'w')
fprint(fid, new_string); 
fclose(fid);

This method will not indent but does allow a slightly better formatting, no matter the structure of your json