[Solved] Why does the following code cause a validation error?class ProductDto { @IsString() name: string;... Why does the following code cause a validation error?class ProductDto { @IsString() name: string; | NestJS

NestJS - Pipes

Why does the following code cause a validation error?

class ProductDto {  @IsString()  name: string;  @IsInt()  quantity: number;}

Input: { "name": "Pen", "quantity": "five" }
ValidationPipe options: { transform: true }

AThe name property is not a string

BThe string "five" cannot be converted to an integer

Ctransform: true disables validation

DValidationPipe does not support nested objects

Step-by-Step Solution

Solution:

Step 1: Analyze input and DTO types
The quantity property expects an integer, but input provides the string "five".
Step 2: Understand transform behavior
transform: true converts types when possible, but "five" cannot convert to a number, causing validation failure.
Final Answer:
The string "five" cannot be converted to an integer -> Option B
Quick Check:
Non-numeric strings fail integer validation even with transform [OK]

Quick Trick: transform converts only valid type strings, not words [OK]

Common Mistakes:

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