title: Query to json firebase object or redux state
body: <p>I'm building my first web app with React, Redux and Firebase, it's about registering the assistance of students (alumnos) to lessons (clases). I've the following database structure (the same in Redux state, this.props).</p>
  
  <pre><code>  "clases" : {
      "-LpQkLyGXEd-Up8hExTx" : {
        "alumnos" : [ "-LpKkSh0E5jiuM0JCCpS", "-LpQi33M-0OSS4Jvup8k" ],
        "fechaClase" : "20-09-2019",
        "profesor" : "Nacho",
        "tema" : "Misión"
      },
      "-LpQmExVsWtW1uPHLK52" : {
        "alumnos" : [ "-LpJvbXb2FjgZvvBv3ei", "-LpKkSh0E5jiuM0JCCpS", "-LpQi33M-0OSS4Jvup8k", "-LpQiDGlRWITax2t6U2A" ],
        "fechaClase" : "22-09-2019",
        "profesor" : "Nacho",
        "tema" : "Bautismo"
      },
      "-LpQqZ_uWu8HxROagVjN" : {
        "alumnos" : [ "-LpKkSh0E5jiuM0JCCpS", "-LpQi33M-0OSS4Jvup8k", "-LpQiPCS2cIK7opMNqyH" ],
        "fechaClase" : "21-09-2019",
        "profesor" : "Manzo, Ignacio",
        "tema" : "Bautismo"
      }
  </code></pre>
  
  <p>I want to select a student (alumno), and know which lessons have made. Do I have to make a double map to the object? Can you give some help?</p>
  
  <p>This is the deployed app <a href="https://metanoia-ic.herokuapp.com/" rel="nofollow noreferrer">https://metanoia-ic.herokuapp.com/</a>
  This is my github repository: <a href="https://github.com/tonicanada/metanoia" rel="nofollow noreferrer">https://github.com/tonicanada/metanoia</a></p>
  
  <p>Thanks!</p>