The type of undefined cannot be assigned to the specified type

Question

The type of undefined cannot be assigned to the specified type

I am currently working on implementing a pie chart (donut series) in Angular. Below are my HTML, CSS, and TypeScript files. I am following this tutorial resource:

Link to CodeSandBox - https://codesandbox.io/s/apx-donut-simple-8fnji?from-embed

import { Component, OnInit, ViewChild } from '@angular/core';
import { ChartComponent } from "ng-apexcharts";

import {
  ApexNonAxisChartSeries,
  ApexResponsive,
  ApexChart
} from "ng-apexcharts";

export type ChartOptions = {
  series: ApexNonAxisChartSeries;
  chart: ApexChart;
  responsive: ApexResponsive[];
  labels: any;
};

@Component({
  selector: 'app-second-page',
  templateUrl: './second-page.component.html',
  styleUrls: ['./second-page.component.css']
})
export class SecondPageComponent implements OnInit {
  @ViewChild("chart") chart: ChartComponent;
  public chartOptions: Partial<ChartOptions>;

  constructor() {
    this.chartOptions = {
      series: [44, 55, 13, 43, 22],
      chart: {
        type: "donut"
      },
      labels: ["Team A", "Team B", "Team C", "Team D", "Team E"],
      responsive: [
        {
          breakpoint: 480,
          options: {
            chart: {
              width: 200
            },
            legend: {
              position: "bottom"
            }
          }
        }
      ]
    };
  }

  ngOnInit(): void {
  }

}

  #chart {
    max-width: 380px;
    margin: 35px auto;
    padding: 0;
  }

  <div id="chart">
    <apx-chart
      [series]="chartOptions.series"
      [chart]="chartOptions.chart"
      [labels]="chartOptions.labels"
      [responsive]="chartOptions.responsive"
    ></apx-chart>
  </div>

I am encountering an undefined issue, although it functions properly in the tutorial. I would appreciate any assistance in resolving this problem.

Error: src/app/second-page/second-page.component.html:32:8 - error TS2322: Type 'ApexNonAxisChartSeries | undefined' is not assignable to type 'ApexAxisChartSeries | ApexNonAxisChartSeries'.
  Type 'undefined' is not assignable to type 'ApexAxisChartSeries | ApexNonAxisChartSeries'.

32       [series]="chartOptions.series"
          ~~~~~~

  src/app/second-page/second-page.component.ts:19:16
    19   templateUrl: './second-page.component.html',
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component SecondPageComponent.


Error: src/app/second-page/second-page.component.html:33:8 - error TS2322: Type 'ApexChart | undefined' is not assignable to type 'ApexChart'.
  Type 'undefined' is not assignable to type 'ApexChart'.

33       [chart]="chartOptions.chart"
          ~~~~~

  src/app/second-page/second-page.component.ts:19:16
    19   templateUrl: './second-page.component.html',
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component SecondPageComponent.


Error: src/app/second-page/second-page.component.html:35:8 - error TS2322: Type 'ApexResponsive[] | undefined' is not assignable to type 'ApexResponsive[]'.
  Type 'undefined' is not assignable to type 'ApexResponsive[]'.

35       [responsive]="chartOptions.responsive"
          ~~~~~~~~~~

  src/app/second-page/second-page.component.ts:19:16
    19   templateUrl: './second-page.component.html',
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component SecondPageComponent.


Error: src/app/second-page/second-page.component.ts:23:23 - error TS2564: Property 'chart' has no initializer and is not definitely assigned in the constructor.

23   @ViewChild("chart") chart: ChartComponent;
                         ~~~~~

✖ Failed to compile.

javascript angular typescript apexcharts donut-chart

Answer 1

Answer №1

While I may not have all the details on the library, I can shed some light on what is causing the compiler to raise concerns.

When you employ the Partial feature in TypeScript, it essentially renders all keys in the subject interface as optional. For instance:

interface SomeInterface {
  key1: string;
  key2: number;
}

type PartialSomeInterface = Partial<SomeInterface>

// is the same as
interface PartialSomeInterface {
  key1?: string;
  key2?: number;
}

// is equivalent to
interface PartialSomeInterface {
  key1: string | undefined;
  key2: number | undefined;
}

By declaring chartOptions as Partial<ChartOptions>, it implies that the object being stored could have zero keys at the minimum, meaning all keys could be missing or undefined, which is considered an acceptable value for chartOptions.

However, when a property from this chartOptions is passed to the <apx-chart> component, the chart component must have | undefined in the type definition for the incoming property. For example, in the case of the series input:

// Component definition required
@Input() series?: ApexAxisChartSeries | ApexNonAxisChartSeries

or

@Input() series: ApexAxisChartSeries | ApexNonAxisChartSeries | undefined

The issue arises when the compiler finds that this condition is not met, and that a value of undefined is not permissible. This typically indicates that the component definition is most likely:

@Input() series: ApexAxisChartSeries | ApexNonAxisChartSeries

In essence, Partial<ChartOptions> might not be a suitable type for chartOptions given the requirements of the child component <apx-chart>.

Despite following the provided documentation/example correctly, this situation can be perplexing.

Here are a couple of suggestions to explore:

If you have predefined all properties of the ChartOptions interface in your chartOptions with initial values, consider removing the Partial. This indicates to the underlying component that each property in chartOptions should be specified, allowing all 4 keys to be passed into the component as done previously
If you still wish to utilize Partial and not define all initial properties of chartOptions, it's worth checking if the version of apx-chart being used is outdated or doesn't align with the demos you referenced

Answer 2

While I may not have all the details on the library, I can shed some light on what is causing the compiler to raise concerns.

When you employ the Partial feature in TypeScript, it essentially renders all keys in the subject interface as optional. For instance:

interface SomeInterface {
  key1: string;
  key2: number;
}

type PartialSomeInterface = Partial<SomeInterface>

// is the same as
interface PartialSomeInterface {
  key1?: string;
  key2?: number;
}

// is equivalent to
interface PartialSomeInterface {
  key1: string | undefined;
  key2: number | undefined;
}

By declaring chartOptions as Partial<ChartOptions>, it implies that the object being stored could have zero keys at the minimum, meaning all keys could be missing or undefined, which is considered an acceptable value for chartOptions.

However, when a property from this chartOptions is passed to the <apx-chart> component, the chart component must have | undefined in the type definition for the incoming property. For example, in the case of the series input:

// Component definition required
@Input() series?: ApexAxisChartSeries | ApexNonAxisChartSeries

or

@Input() series: ApexAxisChartSeries | ApexNonAxisChartSeries | undefined

The issue arises when the compiler finds that this condition is not met, and that a value of undefined is not permissible. This typically indicates that the component definition is most likely:

@Input() series: ApexAxisChartSeries | ApexNonAxisChartSeries

In essence, Partial<ChartOptions> might not be a suitable type for chartOptions given the requirements of the child component <apx-chart>.

Despite following the provided documentation/example correctly, this situation can be perplexing.

Here are a couple of suggestions to explore:

If you have predefined all properties of the ChartOptions interface in your chartOptions with initial values, consider removing the Partial. This indicates to the underlying component that each property in chartOptions should be specified, allowing all 4 keys to be passed into the component as done previously
If you still wish to utilize Partial and not define all initial properties of chartOptions, it's worth checking if the version of apx-chart being used is outdated or doesn't align with the demos you referenced

Answer 3

Answer №2

Check out the latest error message, it will point you to the issue:

Error TS2564: The property 'chart' does not have an initializer and is not explicitly assigned in the constructor.

This error is linked to the TypeScript flag --strictPropertyInitialization which was introduced in version 2.7.

When --strictPropertyInitialization is active, the compiler verifies if all component properties are properly initialized. More details can be found here.

There are multiple solutions to resolve this issue. One approach is to disable the --strictPropertyInitialization flag in the TypeScript compiler options within the tsconfig.json file.

"compilerOptions": {
...
  "strictPropertyInitialization":false
...
}

Answer 4

Check out the latest error message, it will point you to the issue:

Error TS2564: The property 'chart' does not have an initializer and is not explicitly assigned in the constructor.

This error is linked to the TypeScript flag --strictPropertyInitialization which was introduced in version 2.7.

When --strictPropertyInitialization is active, the compiler verifies if all component properties are properly initialized. More details can be found here.

There are multiple solutions to resolve this issue. One approach is to disable the --strictPropertyInitialization flag in the TypeScript compiler options within the tsconfig.json file.

"compilerOptions": {
...
  "strictPropertyInitialization":false
...
}

The type of undefined cannot be assigned to the specified type

Answer №1

Answer №2

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