Grunt not executing sass command - sass

Question

My watch command executes all my tasks except for sass. When I execute grunt sass, I receive the following message error:
Warning:
You need to have ruby and sass installed and in your path for this task to work.
I don't know why this message is showed because I can generate my .css file from the .scss through the Ruby console (sass --watch styles/scss/general.scss:styles/css/general.css), so I have both Ruby and sass installed.
My Gruntfile.js is the following:
module.exports = function(grunt) {
// 1. All configuration goes here
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
concat: {
dist: {
src: [
'js/libs/*.js', // All JS in the libs folder
],
dest: 'js/build/production.js',
}
},
uglify: {
build: {
src: 'js/build/production.js',
dest: 'js/build/production.min.js'
}
},
imagemin: {
dynamic: {
files: [{
expand: true,
cwd: 'images/',
src: ['**/*.{png,jpg,gif}'],
dest: 'images/optimized/'
}]
}
},
sass: {
dist: {
options: {
style: 'compressed'
},
files: {
'styles/css/general.css': 'styles/scss/general.scss'
}
}
},
watch: {
scripts: {
files: ['**/*.{png,jpg,gif}', 'js/libs/*.js'],
tasks: ['imagemin', 'concat', 'uglify'],
options: {
spawn: false,
}
},
sass: {
files: ['css/*.scss'],
tasks: ['sass']
}
}
});
// 3. Where we tell Grunt we plan to use this plug-in.
grunt.loadNpmTasks('grunt-contrib-concat');
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.loadNpmTasks('grunt-contrib-imagemin');
grunt.loadNpmTasks('grunt-contrib-watch');
grunt.loadNpmTasks('grunt-contrib-sass');
grunt.loadNpmTasks('grunt-contrib-compass');
// 4. Where we tell Grunt what to do when we type "grunt" into the terminal.
grunt.registerTask('default', ['concat', 'uglify', 'imagemin', 'watch', 'sass']);
};
My OS is Windows7. Any idea?

Answer 1

Try
var config = {
app: 'app',
dist: 'dist'
};
grunt.initConfig({
sass: {
dist: {
options: {
style: 'compressed'
},
files: [{
cwd: 'styles/scss/',
src: '*.scss',
dest: 'styles/css/',
ext: '.css'
}],
},
watch: {
sass: {
files: ['styles/scss/{,*/}*.scss'],
tasks: ['sass'],
options: {
livereload: true
}
}
}
};
and would be better to place all the grunt.loadNpmTasks at the top before the grunt.initConfig