title: Observable value inside subscribe is undefined when chaning observables
body: <p>I have a function from a certain library that returns an Observable that I want to call from another function. I have a need to propagate that Observable into multiple function calls. Here is how my code is structured:</p>
  <pre><code>extractSignature = (xml, signatureCount = 1) =&gt; {
      const observ = this.generateDigest(signedContent, alg).pipe(map(digest =&gt; {
              const sigContainer = {
                  alg: alg,
                  signature: signatureValue,
                  signedContent: signedContent,
                  digest: digest
              };
              console.log('sigContainer inside pipe: ');
              console.log(sigContainer);
              return sigContainer;
          }));
  
          return observ;
  }
  
  dissasemble(xml): Observable&lt;SignatureContainerModel[]&gt; {
      const observables: Observable&lt;any&gt;[] = [];
          for (let i = 1; i &lt;= count; i++) {
              const extractSigObservable = this.extractSignature(xml, i);
  
              console.log('extractSigObs inside pipe: ');
              console.log(extractSigObservable);
  
              const observ = extractSigObservable.pipe(map(sigContainer =&gt; {
                  console.log('sigContainer inside pipe: ');
                  console.log(sigContainer);
  
                  const hashContainers: HashContainerModel[] = [];
                  const hashContainer: HashContainerModel = new HashContainerModel();
                  hashContainer.digestAlgorithm = sigContainer.alg;
                  hashContainer.bytes = sigContainer.digest;
                  hashContainers.push(hashContainer);
                  const signatureContainer: SignatureContainerModel = {
                      hashContainers: hashContainers,
                      signature: sigContainer.signature
                  };
  
                  console.log('observable inside pipe: ');
                  console.log(observ);
              }));
  
  
              observables.push(observ);
          }
  
          return forkJoin(observables);
  }
  
  verify() {
      this.sigExec.dissasemble(this.fileContent).subscribe((signatureContainers: SignatureContainerModel[]) =&gt; {
                  // signatureContainers is [undefined] here
                  console.log('Sig Containers: ');
                  console.log(signatureContainers);
                  this.verifyHash(signatureContainers);
              });
  }
  </code></pre>
  <p><em>signatureContainers</em> variable is [undefined] inside the subscribe. I'm not sure what the problem is since when I check all the logs that I wrote inside map functions they seem fine</p>