Usage

For TypeORM repo:

const repo = getRepository(Test1Entity);
const queryHelper = new QueryHelper(repo);

const result = await queryHelper.selectSpecific({
    select: {
        selected1: (el) => el.id,
        selected2: (el) => el.test2.id,
        selected3: (el) => el.test2.test1.id,
    },
    where: {
        condition: {
            pathGetter: (el) => el.test2.test1.id,
            operation: Equals(1),
        },
    },
});

Result will have type:

const result: {
    name1: typeof el.name,
    name2: typeof el.test1.name,
    name3: typeof el.test1.test2.name,
    id: typeof el.test1.id
    }[]

Example of getter:

(el)=> el.<association_1>.<association_2>.<column>

Last field of getter is column, and not association.

Getter fields that are not the last one are associations, and not getters.

Requirements:

1. TypeORM
2. Properly defined entities

Example:

export class Entity1 {
    @PrimaryGeneratedColumn()
    id: number

    // column
    @Column()
    field1: number

    // association
    @ManyToOne(() => Entity2, (el)=>el.return_field_1)
    field2: Entity2

    // association
    @OneToMany(() => Entity3, (el)=>el.return_field_2)
    field2: Entity3[]

    // association
    @OneToOne(() => Entity4, (el)=>el.return_field_3)
    field3: Entity4
}

Why?

1. reason:

   If you use rename functionality (F2) of Visual Code Editor to rename field of an class of interface, it will not take strings into consideration. If some strings have parts that need to be matching those fields you will need to manualy change those parts of strings. Solution? Instead of using strings, use different types of writing down the query which will be updated by rename functionality (F2).

2. reason:

   When you use query.getRawMany() the return type is unknown[], so you have to cast it. That requires to define your interface and make sure it maches fields specified in query. This code does not require that, because return type is defined in manner that it is being picked up from passed parameters.

Bonus

const path = getPath<Entity1>((el) => el.field1.field2.field3)

// path:  ["field1", "field2", "field3"]

Example 1

const repo = getRepository(Test1Entity);

const queryHelper = new QueryHelper(repo);

const found = await queryHelper.SelectSpecific(
    {
        field1: (el) => el.test2.test1.id,
        field2: (el) => el.test2.id,
        field3: (el) => el.id,
    },
    {
        and: [
            {
            or: [
                {
                condition: {
                    pathGetter: (el) => el.field1,
                    operation: {
                        value: 1,
                        stringMaker: (alias, field, varName) => `${alias}.${field} < ${varName}`,
                        },
                },
                },
                {
                condition: {
                    pathGetter: (el) => el.field1,
                    operation: {
                        value: 0,
                        stringMaker: (alias, field, varName) => `${alias}.${field} > ${varName}`,
                    },
                },
                },
            ],
            },
            {
            condition: {
                pathGetter: (el) => el.test2.field2,
                operation: {
                    value: 1,
                    stringMaker: (alias, field, varName) => `${alias}.${field} = ${varName}`,
                },
            },
            },
        ],
        }
    );
}

Example 2.

import { Equals, OperatorData } from "type-safe-select";

const operatorData1 = Equals(1);

// It returns same as the following:
const operatorData2: OperatorData<number> = {
    value: 1,
    stringMaker: (alias, field, varName) => `${alias}.${field} = ${varName}`,
};

Example 3.

const result = await queryHelper.selectGroupBy({
    select: {
        selected1: (el) => el.groupBy.field1,
        selected2: (el) => el.groupBy.field2,
        count1: (el) => el.count,
        sum1: (el) => el.sum.field2,
    },
    where: {
        condition: {
            pathGetter: (el) => el.field1,
            operation: Equals("D"),
        },
    },
});