Unable to resolve signature of property decorator when called as an expression

Question

import { isEmail, isEmpty, isPhoneNumber, Length } from "class-validator"
import { Field, InputType } from "type-graphql";

@InputType()
export class RegisterInput {
    @Field()
    @Length(2, 15, { message: "Username Must Be At Least 2 characters" })
    username?: string;

    @Field()
    @isEmail()
    email?: string;

    @Field()
    @Length(1, 20)
    @isPhoneNumber()
    phoneNumber?: string;

    @isEmpty()
    password?: string

}

The thing is @isEmail() and @isPhoneNumber() and @isEmpty() throw the same error:

Unable to resolve signature of property decorator when called as an expression.
  This expression is not callable.
    Type 'Boolean' has no call signatures.ts(1240)

Please help me out I’ve been stuck with this bug the whole day

user6749601user6749601 · Accepted Answer · 2021-04-11 13:20:08Z

You have to write those Decorators with a capital letter. TypeScript is case sensitive:

import { IsEmail, IsEmpty, IsPhoneNumber, Length } from "class-validator";

@Field()
@IsEmail()
email?: string;

@Field()
@Length(1, 20)
@IsPhoneNumber()
phoneNumber?: string;

@IsEmpty()
password?: string

Nevermind, I don't know anyone who did not run in such self made problems. 😉 You're welcome. 🙂 — user6749601, Apr 11, 2021 at 14:10

score 1 · Accepted Answer · 2022-02-25 09:16:11Z

1

For people who come here by googling the error message.

I had this error because I was importing the decorator from a .js file. Converting it to TypeScript resolved the issue for me.

answered Feb 25, 2022 at 9:16

Andrey Mikhaylov – lolmaus

23.2k6 gold badges84 silver badges135 bronze badges

GorgseneggerGorgsenegger 7,4264 gold badges52 silver badges89 bronze badges · Accepted Answer · 2022-05-09 06:33:13Z

My problem was that I accidentally added a ; after the decorator:

@minimumValue("quantity", 5);
async getItems(): Promise<Item[]> {
...

This results in TS1240: Unable to resolve signature of property decorator when called as an expression..

So the correct syntax is without the ;:

@minimumValue("quantity", 5)
async getItems(): Promise<Item[]> {
...

Hugo VinhalHugo Vinhal 3041 silver badge15 bronze badges · Accepted Answer · 2023-09-30 23:08:42Z

0

You might need to add this property to your tsconfig.json file, under the compilerOptions property:

"experimentalDecorators": true

Kudos to Technical Rajni for the youtube video solution, here.

answered 1 hour ago

Hugo Vinhal

3041 silver badge15 bronze badges

Bruno CrosierBruno Crosier 6529 silver badges14 bronze badges · Accepted Answer · 2022-04-07 13:39:25Z

-1

your problem is because you tried to invoke the class decorator by adding () at the end of it (@InputType())

instead you should just do @InputType

answered Apr 7, 2022 at 13:39

Bruno Crosier

6529 silver badges14 bronze badges

Unable to resolve signature of property decorator when called as an expression