Updating three.js texture throughthe dat.gui dropdown - three.js

Question

I have loaded different textures using textureLoader and I am trying to update them using dat.gui controls.
Why is the code below not working?
gui.add(mesh.position, "y", -1, 1, 0.1);
gui.add(mesh.material, "map", { alpha: alphaTexture, color: colorTexture, normal: normalTexture })
.onChange(() => {
mesh.material.needsUpdate = true;
console.log("updated");
});
It gives this error:
"Uncaught TypeError: m is undefined" [error][1]

Answer 1

After some tweaking, I found that the values of object(or array) in the third argument only supports string types, so passing a object as a value would not work.
This is the closest workaround that I could think of..
/* GUI options */
const guiOptions = {
mesh_material_map: "color",
};
/* Textures */
const textureLoader = new THREE.TextureLoader(loadingManager);
const colorTexture = textureLoader.load("/textures/door/color.jpg");
const alphaTexture = textureLoader.load("/textures/door/alpha.jpg");
const normalTexture = textureLoader.load("/textures/door/normal.jpg");
const guiTextureHash = {
color: colorTexture,
alpha: alphaTexture,
normal: normalTexture,
};
/* Add to gui */
gui.add(guiOptions, "mesh_material_map", Object.keys(guiTextureHash)).onChange((value) => {
mesh.material.map = guiTextureHash[value];
mesh.needsUpdate = true;
console.log("updated", value);
});

Answer 2

I found your topic looking for a texture picker. It's probably a little away from your starting point but could help some other. I finally made a simple texture picker with a dropdown selection key with dat.gui. The goal is to be able to change on the fly my matcap texture, going through an array of loaded texture.
const gui = new dat.GUI()
const textureLoader = new THREE.TextureLoader()
const myMatCap = [
textureLoader.load('./textures/matcaps/1.png'),
textureLoader.load('./textures/matcaps/2.png'),
textureLoader.load('./textures/matcaps/3.png')
]
const parameters = {
color: 0xff0000,
matCapTexture: 0
}
const updateAllMaterials = () => {
scene.traverse( (child)=>{
if(child instanceof THREE.Mesh && child.material instanceof THREE.MeshMatcapMaterial) {
child.material.matcap = myMatCap[ parameters.matCapTexture]
child.material.needsUpdate = true
}
})
}
gui.add(parameters, 'matCapTexture', {
terracotta: 0,
grey: 1,
chrome: 2,
}).onFinishChange(()=>{
updateAllMaterials()
})
let mesh = new THREE.Mesh(
geometry,
new THREE.MeshMatcapMaterial({
side: THREE.DoubleSide,
matcap: myMatCap[ parameters.matCapTexture ]
})
);
scene.add(mesh)