Builder pattern with generics in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic Builder class.

Typescript

class Builder<[1]> {
  private value: T;
  constructor(initialValue: T) {
    this.value = initialValue;
  }
}

Drag options to blanks, or click blank then click option'

AK

BV

CT

DU

Attempts:

3 left

💡 Hint

Common Mistakes

Using a lowercase letter for the generic type parameter.

Not matching the generic parameter with the constructor argument.

The generic type parameter T is used to define the type for the Builder class.

2fill in blank

medium

Complete the method to set a new value in the Builder class.

Typescript

setValue(newValue: T): this {
  this.value = [1];
  return this;
}

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AnewValue

Bvalue

Cthis.value

DnewVal

Attempts:

3 left

💡 Hint

Common Mistakes

Using an undefined variable like value instead of newValue.

Trying to assign this.value to itself.

The method should assign the parameter newValue to the internal value property.

3fill in blank

hard

Fix the error in the build method to return the stored value.

Typescript

build(): [1] {
  return this.value;
}

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Avoid

BT

Cany

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using void which means no return value.

Using a concrete type like number which may not match T.

The build method should return the generic type T which is the type of the stored value.

4fill in blank

hard

Fill both blanks to create a generic Builder method that updates a property and returns the builder.

Typescript

setProperty<K extends keyof T>(key: [1], value: T[K]): this {
  this.value[key] = [2];
  return this;
}

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AK

Bkey

Cvalue

DT

Attempts:

3 left

💡 Hint

Common Mistakes

Using key as the type instead of the parameter name.

Assigning key instead of value to the property.

The method uses K as the key type and assigns value to the property.

5fill in blank

hard

Fill all three blanks to create a generic Builder class with a static create method.

Typescript

class Builder<[1]> {
  private value: T;
  private constructor(initialValue: T) {
    this.value = initialValue;
  }

  static create<[2]>(initialValue: [3]): Builder<U> {
    return new Builder<U>(initialValue);
  }
}

Drag options to blanks, or click blank then click option'

AT

BU

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same generic parameter name for both class and static method.

Mismatching the generic parameter in the static method signature.

The class uses T as the generic type. The static method defines its own generic U and uses it for the parameter and return type.