Nestjs swagger array of strings with one parameter

Question

When I send only one parameter, I got query result like string, not like string[]. This happened only from UI swagger, if I send from Postman - it works good.

I just want send from swagger-ui one parameter and got array of strings, not a single string.

How I can fix it? Help me please.

Example1: send one parameter and in my controller I got string like '25'

Example2: when I send 2 parameters in controller I can see array of strings ('25', '21')

export class List {
  @ApiProperty({ isArray: true, type: String, required: false })
  @IsOptional()
  public categories?: string[];
}

Have you tried using the type like this @ApiProperty({ type: [String] })? — Farista Latuconsina
– Farista Latuconsina, Commented Dec 3, 2022 at 8:37
@Farista Latuconsina I just tried, but got the same result. @ApiProperty({ type: [String] }) @ApiProperty({ type: () => [String] }) @ApiProperty({ type: () => [String], isArray: true }) — Maksym Shafarenko
– Maksym Shafarenko, Commented Dec 3, 2022 at 10:51

paypes · Accepted Answer · 2022-12-06 09:46:50Z

6

when you fill a single category the query param will be translated as a string while when you fill in several categories understand it as a array.

to solve this problem I added in DTO :

@Transform(({ value }) => (Array.isArray(value) ? value : Array(value)))

I force the cast to array

edited Dec 6, 2022 at 9:46

answered Dec 6, 2022 at 9:45

paypes

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1 Comment

Maksym Shafarenko Over a year ago

As I understood swagger library can't fix that, so your answer good for me. Thanks.

Malkavianson · Accepted Answer · 2022-12-05 17:28:15Z

1

You should try to spread your parameter in a const in services edit:

I don't know how to explain in formal words, but a array of strings of one item, for JAVASCRIPT, seems with the same thing as one string value.

Because array is not a type, but a form of a type....

So, if you, in your controller, before do anything with it, you redeclare as:

    @Get(":id")
    findManybyId(@Param("id") id: string[]) {
        const idArray = [...id];
        return await this.service.findManyById(idArray);
    }

It will solve your problem about being an array

old answer:

You should try to change in your controller where you make your input decorator.

in your case, i don't know if you are using ID to get, but you must to do as the example:

   @ApiOperation({
       summary: "Get many categories by ID",
   })
   async getMany(
       @Param("id") ids: string[],
   ) {
       return await this.categoriesService.getMany(id);
   }

edited Dec 5, 2022 at 17:28

answered Dec 3, 2022 at 22:35

Malkavianson

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3 Comments

Maksym Shafarenko Over a year ago

can you write an example or explain more please?

Maksym Shafarenko Over a year ago

I don't want write some logic in controller. Thanks

unify Over a year ago

If you do [,,,id] where id is a string and not an array (E.g. "hello"), you'll get the value of the string split (["h","e","l","l","o"])

Lê Tiến Đạt · Accepted Answer · 2024-09-11 08:38:28Z

I have the same problem with you.

I decide to create a utils transform called toArray.

Code:

    export function ToArray(): (target: any, key: string) => void {
    return Transform((params: TransformFnParams) => {
          const { value } = params;

          if (Array.isArray(value)) {
              return value;
           }

          if (typeof value === 'string') {
              return value.split(',').map(item => item.trim());
          }
       
          return [];
         });
      }

So when i need to transform i just need import ToArray any where need to transform to Array.

    @ApiProperty({ description: 'List of category IDs', example: ['47b32970-4997-4364-91b6-4b5533941307', '620b7c84-6d63-492e-8abb-7606e04a375c'], required: false })
    @ToArray()
    @IsArray()
    categories?: string[];

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