Ionic 3 Login Authentication Using API - Cannot read property 'json' of null

Question

I am doing authentication in Ionic 3 using API but In the login process, it is showing error: Cannot read property \'json\' of null

This is my provi

Answer 1

Also, wouldn't it be easier to just return observable instead of a promise?

return this.http.post(apiUrl + type, JSON.stringify(credentials), {headers: headers});