how to change the global variable inside a scss mixin

theme-variables.scss

//---------------------------------------------------------
//Declare a global variable and set it to red color
//---------------------------------------------------------
$fg-primary-text: red; 

//---------------------------------------------------------
//below @mixin is used in styles.scss to pass the custom-theme
//---------------------------------------------------------
@mixin cache-theme-colors($theme) {
   @include set-global-variables($theme);
}

//---------------------------------------------------------
//local mixin to set the global-variable from the $theme using !global flag
//---------------------------------------------------------
@mixin set-global-variables($theme: $theme, $fg-primary-text: $fg-primary-text) {
 $foreground: map-get($theme, foreground); //get foreground from the theme
 $fg-primary-text: mat-color($foreground, text) !global; //get the text color from the theme and set it here using the !global flag

}

component.scss

@import "../../../../assets/themes/theme-variables.scss";

.text-color {
    color: $fg-primary-text;  //use the variable (but it is still red)
}

But the color is still red My question is: how to set the global variable in scss and change it inside a mixin/function and use it in any component.scss

You will need a mixin function in your component.scss.

And then have a @include in your main.scss file.

component.scss

@mixin text-color-mixin($theme) {
  $is-dark-theme: map-get($theme, is-dark);
  .text-color {
    color: if($is-dark-theme, red, blue);
  }
}

main.scss

@import ..<path to file>.../component.scss
...
<Other code>
...
@include  text-color-mixin($theme);

To find out more on how you can structure your angular project themes you can look at https://github.com/angular/material.angular.io

This is the official repo for the angular material io documentation site.

EDIT

I think this also answers your question

How to manipulate scss variables in Angular2 components

Atlast I've found a solution, and I'm sharing here for those who need it.

Note: I know it's very long.. but read patiently you may get something or correct me If I'm doing anything wrong.

First start from the theme.service

theme.service.ts

import { Injectable } from '@angular/core';
import { OverlayContainer } from '@angular/cdk/overlay';

@Injectable({ providedIn: 'root' })
export class ThemeService {

  constructor(private overlayContainer: OverlayContainer) {}

  currentThemeNAME: string = "light-theme";
  //DEFAULT_THEME
  private defaultThemeNAME: string = "light-theme";
  setDefaultTHEME() {
    this.setTHEME(this.defaultThemeNAME);
  }

  //LIGHT_THEME
  private lightThemeNAME: string = "light-theme";
  setLightTHEME() {
    this.setTHEME(this.lightThemeNAME);
  }

  //DARK_THEME
  private darkThemeNAME: string = "dark-theme";
  setDarkTHEME() {
    this.setTHEME(this.darkThemeNAME);
  }

  //TO_SET_THE_THEME
  setTHEME(themeNAME: string) {
    console.log(themeNAME);
    this.currentThemeNAME = themeNAME;
    this.overlayContainer.getContainerElement().classList.add(this.currentThemeNAME);
  }

  //TO_CYCLE_THE_THEME
  cycleTHEME() {
    switch (this.currentThemeNAME) {
      case this.lightThemeNAME:
        this.setDarkTHEME();
        break;
      case this.darkThemeNAME:
        this.setLightTHEME();
        break;
    }
  }

}

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { NgModule } from '@angular/core';
import { RouterModule } from '@angular/router';
import { FlexLayoutModule } from '@angular/flex-layout';

//CORE-SERVICES
import { ThemeService } from './core/services/theme.service';

@NgModule({
  entryComponents: [...],
  declarations: [...],
  exports: [...],
  imports: [...],


  providers: [ ThemeService ], //<----Important

  bootstrap: [AppComponent],
})

export class AppModule {
  //important
  constructor(private themeSRVC: ThemeService) {
    this.themeSRVC.setDefaultTHEME(); //<----Important
  }

}

Lets Assume I've 2 themes:

1) light-theme.scss

// define 3 theme color
// mat-palette accepts $palette-name, default, lighter and darker variants

$light-theme-primary: mat-palette($mat-grey, 500, 100, 700);
$light-theme-accent: mat-palette($mat-pink);
$light-theme-warn: mat-palette($mat-red);

// create theme (use mat-dark-theme for themes with dark backgrounds)
$light-theme: mat-light-theme( $light-theme-primary, $light-theme-accent, $light-theme-warn);

2) dark-theme.scss

// define 3 theme color
// mat-palette accepts $palette-name, default, lighter and darker variants

$dark-theme-primary: mat-palette($mat-grey, 900, 700, 900);
$dark-theme-accent: mat-palette($mat-blue-grey);
$dark-theme-warn: mat-palette($mat-red);

// create theme (use mat-dark-theme for themes with dark backgrounds)
$dark-theme: mat-dark-theme($dark-theme-primary, $dark-theme-accent, $dark-theme-warn);

styles.scss

/* You can add global styles to this file, and also import other style files */

@import './assets/fonts/roboto/stylesheet.css';
@import './assets/icons/material-icons/v42/stylesheet.css';

//important
@import '~@angular/material/theming';

//important: always include only once per project
@include mat-core();

//important: import our custom theme files here
@import './assets/themes/light-theme.scss';
@import './assets/themes/dark-theme.scss';

//important: import the theme cacher
@import './assets/themes/register_components.scss';

html,
body {
  height: 100%;
  padding: 0px;
  margin: 0px;
  font-family: Roboto;
}

// to set this theme: 
// set yout component's root element's class
// example-1: <body class="dark-theme"> ... </body>
// example-2: <form [ngClass]="themeSRVC.currentThemeNAME"

.light-theme {
  @include angular-material-theme($light-theme); //set material_theme
  @include set-components-theme($light-theme); //cache_theme
}

// to set this theme: 
// set yout component's root element's class
// example-1: <body class="dark-theme"> ... </body>
// example-2: <form [ngClass]="themeSRVC.currentThemeNAME"

.dark-theme {
  @include angular-material-theme($dark-theme); //set material_theme
  @include set-components-theme($dark-theme); //cache_theme
}

//...similarly register your other themes here

register_components.scss

@import '~@angular/material/theming';
@import '../src/app/erp/security/erp-login/erp-login.component.scss';
@import '../src/app/erp/dashboard/dashboard.component.scss';
@mixin set-components-theme($theme) {
  //###################################################################################
  //---STEP-(1/3): EXTRACT_PALLETE_AND_COLORS----------
  //https://github.com/angular/material2/blob/master/src/lib/core/theming/_palette.scss
  //https://github.com/angular/material2/blob/master/src/lib/core/ripple/_ripple.scss
  //###################################################################################
  //---01-PRIMARY---------------------
  $primary-palette: map-get($theme, primary); //<---
  $primary-color: mat-color($primary-palette, default);
  $primary-light: mat-color($primary-palette, lighter);
  $primary-dark: mat-color($primary-palette, darker); //<---
  //---02-ACCENT----------------------
  $accent-palette: map-get($theme, accent); //<---
  $accent-color: mat-color($accent-palette, default);
  $accent-light: mat-color($accent-palette, lighter);
  $accent-dark: mat-color($accent-palette, darker); //<---
  //---03-WARN------------------------
  $warn-palette: map-get($theme, warn); //<---
  $warn-color: mat-color($warn-palette, default);
  $warn-light: mat-color($warn-palette, lighter);
  $warn-dark: mat-color($warn-palette, darker); //<---
  //---04-FOREGROUND------------------
  $foreground-palette: map-get($theme, foreground); //<---
  $fg-base: mat-color($foreground-palette, base); //full_black or full_white
  $fg-primary-text: mat-color($foreground-palette, text);
  $fg-secondary-text: mat-color($foreground-palette, secondary-text);
  $fg-hint-text: mat-color($foreground-palette, hint-text);
  $fg-disabled: mat-color($foreground-palette, disabled);
  $fg-disabled-button: mat-color($foreground-palette, disabled-button);
  $fg-disabled-text: mat-color($foreground-palette, disabled-text);
  $fg-divider: mat-color($foreground-palette, divider);
  $fg-dividers: mat-color($foreground-palette, dividers);
  $fg-elevation: mat-color($foreground-palette, elevation);
  $fg-icon: mat-color($foreground-palette, icon);
  $fg-icons: mat-color($foreground-palette, icons);
  $fg-slider-min: mat-color($foreground-palette, slider-min);
  $fg-slider-off: mat-color($foreground-palette, slider-off);
  $fg-slider-off-active: mat-color($foreground-palette, slider-off-active); //<--
  //---05-BACKGROUND------------------
  $background-palette: map-get($theme, background); //<---
  $bg-color: mat-color($background-palette, background);
  $bg-status-bar: mat-color($background-palette, status-bar);
  $bg-app-bar: mat-color($background-palette, app-bar);
  $bg-hover: mat-color($background-palette, hover);
  $bg-card: mat-color($background-palette, card);
  $bg-dialog: mat-color($background-palette, dialog);
  $bg-disabled-button: mat-color($background-palette, disabled-button);
  $bg-raised-button: mat-color($background-palette, raised-button);
  $bg-focused-button: mat-color($background-palette, focused-button);
  $bg-selected-button: mat-color($background-palette, selected-button);
  $bg-selected-disabled-button: mat-color($background-palette, selected-disabled-button);
  $bg-disabled-button-toggle: mat-color($background-palette, disabled-button-toggle);
  $bg-unselected-chip: mat-color($background-palette, unselected-chip);
  $bg-disabled-list-option: mat-color($background-palette, disabled-list-option); //<---
  //---COMMON_COLORS---------------
  //fetch from the theme directly using the is_dark_mode flag
  $is-dark-theme: map-get($theme, is-dark); //<---
  //primary_text
  $fg-dark-primary-text: rgba(black, 0.87);
  $fg-light-primary-text: white;
  $fg-primary-text-inverse: if($is-dark-theme, $fg-dark-primary-text, $fg-light-primary-text); //<---
  //secondary_text
  $fg-dark-secondary-text: rgba(black, 0.54);
  $fg-light-secondary-text: rgba(white, 0.7);
  $fg-secondary-text-inverse: if($is-dark-theme, $fg-dark-secondary-text, $fg-light-secondary-text); //<---
  //disabled_text
  $fg-dark-disabled-text: rgba(black, 0.38);
  $fg-light-disabled-text: rgba(white, 0.5);
  $fg-disabled-text-inverse: if($is-dark-theme, $fg-dark-disabled-text, $fg-light-disabled-text); //<---
  //dividers
  $bg-dark-dividers: rgba(black, 0.12);
  $bg-light-dividers: rgba(white, 0.12);
  $bg-dividers-inverse: if($is-dark-theme, $bg-dark-dividers, $bg-light-dividers); //<---
  //focused
  $bg-dark-focused: rgba(black, 0.12);
  $bg-light-focused: rgba(white, 0.12);
  $bg-focused-inverse: if($is-dark-theme, $bg-light-focused, $bg-light-focused); //<---
  //---DERIVED_COLORS--------------
  $_bg-ripple: rgba($fg-base, 0.1); //SPEC
  $_bg-list-item: $bg-card;
  $_scrollbar-bg: rgba($fg_icon, .4);
  $_scrollbar-fg: rgba($fg_icon, .05);
  $_scrollbar-hover-bg: rgba($fg_icon, .16);
  $_scrollbar-hover-fg: rgba($fg_icon, .20); //<----
  //###################################################################################
  //---STEP-(2/3): CREATE_GLOBAL_CLASSES_THAT_DEPEND_ON_THE_ABOVE_THEME_COLORS--
  //###################################################################################
  //++++++MAT-LIST-ITEM++++++++++++++++++++++++++++
  .mat-list-item {
    background-color: $_bg-list-item;
  }
  .mat-list-item.selected {
    background-color: $primary-light;
  }
  .mat-list-icon {
    color: $fg_icon;
  } //<---
  //###################################################################################
  //---STEP-(3/3): PASS_REQUIRED_COLORS_TO_THE_COMPONENTS-----(note: not the $theme)
  //###################################################################################
  //---Pass_Colors_required_by_the_DashboardComponent
  @include dashboard-component-theme( //---
    $fg-primary-text, $fg-secondary-text, //---
    $fg-primary-text-inverse, $fg-secondary-text-inverse, //---
    $_bg-ripple); //<--

  //---Pass_Colors_required_by_the_erp-Component
  @include erp-component-theme($fg-primary-text, $fg-secondary-text);

 //similarly register all your components here and pass only the required colors
} //--------------------------------------------

dashboard.component.scss

@import '~@angular/material/theming';

//colors_passed_by_the register_component.scss

@mixin dashboard-component-theme(    
    $fg-primary-text, $fg-secondary-text, 
    $fg-primary-text-inverse, $fg-secondary-text-inverse, 
    $_bg-ripple) {
 
    //Classes for component's html
    
    .sidenav-header-primary-text {
        color: $fg-primary-text-inverse;
        font-size: 18px;
        line-height: 28px;
        margin-bottom: 8px;
    }
    
    .sidenav-header-secondary-text {
        color: $fg-secondary-text-inverse;
        font-size: 15px;
        line-height: 15px;
        margin-bottom: 2px
    }
    
    .list-item-primary-text {
        color: $fg-primary-text;
    }
    
    .list-item-secondary-text {
        color: $fg-secondary-text;
    }
    
}

dashboard.component.ts

@Component({
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: ['./dashboard.component.scss'],

})
export class DashboardComponent implements OnInit {

  //###-Important: include the ThemeService
  constructor(private themeSRVC: ThemeService) {
    //...
  }
 
  //...
  
   //---
}

dashboard.component.html

<!-- Important set [ngClass] of the root element from the themeSRVC -->

<mat-sidenav-container [ngClass]="themeSRVC.currentThemeNAME">


  <!-- .... -->

  <!-- Include the classes from the component's scss -->

  <h4 class="list-item-primary-text" mat-line>456</h4>
  <p class="list-item-scondary-text" mat-line>123</p>


  <!-- .... -->

</mat-sidenav-container>

That's It..!

来源：https://stackoverflow.com/questions/53922711/how-to-change-the-global-variable-inside-a-scss-mixin

标签

Sass

angular-material2

scss-mixins