我如何从 firebase 实时数据库中获取离子的单个值

Question

async incrementTuts(key) {
 let newData= {'tutsApplied':this.tutsApplied+1} 
 let newInfo = firebase.database().ref('thisis/'+this.route.snapshot.paramMap.get('key')).update(newData);
}

I want to increment tutsApplied on firebase realtime database using ionic 4. how can i acheive that.

Corrected image:

update:

i have used

let key = this.route.snapshot.paramMap.get('key');
let ref = firebase.database().ref(`thisis/${key}/tutsApplied`);
ref.transaction((current) => {
  return (current || 0) + 1;
});

but new field is created under undefined as shown in image. i dont want to create new field. and how can i print current value in console?

Answer 1

It sounds like you're looking to write a new value for a property based on its current value. To do that, you'd use a transaction .

Something like:

let key = this.route.snapshot.paramMap.get('key');
let ref = firebase.database().ref(`thisis/${key}/tutsApplied`);
ref.transaction((current) => {
  return (current || 0) + 1;
});