UIManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class UIManager : MonoBehaviour
{
    List<GameObject> points;
    List<GameObject> lines;

    public Transform pointsParent;
    public Transform linesParent;
    public GameObject button;
    public GameObject line;

    string chosen1 = "";
    string chosen2 = "";

    public CanvasManager3D CM;

    enum UIState
    {
        none,
        createLine
    }

    UIState state = UIState.none;
    
    // Start is called before the first frame update
    void Start()
    {
        points = new List<GameObject>();
        lines = new List<GameObject>();
    }

    // Update is called once per frame
    void Update()
    {
        switch (state)
        {
            case UIState.none:
                break;
            case UIState.createLine:
                if(!chosen1.Equals("") && !chosen2.Equals(""))
                {
                    createLine();
                }
                break;
        }
    }

    public void createPoint()
    {
        string n = CM.createPoint();
        GameObject tmp = Instantiate(button);
        tmp.transform.SetParent(pointsParent);
        points.Add(tmp);
        tmp.transform.localPosition = new Vector3(50 + 40 * (points.Count - 1), 0, 0);
        tmp.GetComponentInChildren<Text>().text = n;
        tmp.GetComponent<Button>().onClick.AddListener(delegate(){ chooseObject(n); });
    }

    public void createLineButton()
    {
        state = UIState.createLine;
    }

    void createLine()
    {
        string n = CM.createLine(chosen1, chosen2);
        chosen1 = "";
        chosen2 = "";
        GameObject tmp = Instantiate(line);
        tmp.transform.SetParent(linesParent);
        lines.Add(tmp);
        tmp.transform.localPosition = new Vector3(50 + 40 * (lines.Count - 1), 0, 0);
        tmp.GetComponentInChildren<Text>().text = n;
        state = UIState.none;
    }

    public void chooseObject(string obj)
    {
        if (chosen1.Equals(""))
            chosen1 = obj;
        if (!chosen1.Equals("") && !chosen1.Equals(obj) && chosen2.Equals(""))
            chosen2 = obj;
    }

    public void LineButton()
    {
        if(state == UIState.none)
        {

        }
    }
}