Please ensure the subscription has completed before proceeding with the loop

I am currently working on an Angular application that retrieves data from an API and uses one of its parameters from a looped array. The issue I'm facing is that the data is pushed in a random order due to the continuous looping without waiting for the subscription to finish before pushing the result.


    let parameterArray = ["a", "b", "c"]
    let finalData = []
    
    parameterArray.forEach(parameter => {
       let tmpValue = /* Implement logic for parameter data transformation */
       forkJoin(this.apiService.getApiData(tmpValue)).subscribe(response => {
          let transformedData = /* Data processing logic */
          finalData.push(transformedData);
       })
    })

Calling the API multiple times is not ideal, but my main goal right now is to find a way to iterate through the parameterArray and push the transformed data in the correct order. Any help would be greatly appreciated!

Answer №1

When dealing with an array of observables, a ForkJoin comes in handy. Typically, these observables are created to transform an array using the "map" method.

forkJoin(
   this.parameterArray.map(x=>{
     tmpValue=..perform some operation on x..
     return this.apiService.getApiData(tmpValue)
   }  //the result is an array of observables
).subscribe(res:any[])=>{
   - In res[0], you have the response from this.apiService.getApiData(tmpvalue) to calculate with "a".
   - In res[1], you have the response from this.apiService.getApiData(tmpvalue) to calculate with "b".
   - In res[2], you have the response from this.apiService.getApiData(tmpvalue) to calculate with "c".

})

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