How to correctly handle data object from REST API using fetch in React





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I have a React app that receives an object from WordPress site using fetch() over rest api (v2/posts).



The object contains an "acf" entry which holds ~30 sub entries: some arrays and some are objects. All generated with Advanced Custom Field plugin.



The application is updating this data (using this.state) and the server (fetch/post) upon user request. All is working. I am not using express, redux and the like.



My current problem is that I cannot access the internals of the "acf" entry in render() function, while I can access it within the fetch response.
I would like to be able to acccess


 cpt['acf']['entry']['subentry']

using the entry's names. But I get "cannot access property of undefined..."

Example:





// In constructor:
// this.state = {
// isLoading: false, title:"", terms:, cpt:
// }
...
fetch(url)
.then(response => {
if (response.ok)
return response.json()
throw new Error('fetchTerm: Something went wrong ...')
})
.then(cpt => {
var terms = Object.entries(cpt['acf'])
var title = Object.values(cpt['title'])

this.setState({cpt, terms, title, isLoading: false})
.then( () => {
console.log("title",this.state.cpt['title'])
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // shows ok
})

return (true) // void - no one is looking...
})
//...
render(){
if (this.state.isLoading)
return (Loading)
// occurs only after fetch resturn and this.state variables are instanciated
console.log("title", this.state.title) // shows OK
console.log("FAIL", this.state.cpt['title']) // cannot access property of NULL/Undefined...
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // same problem
}



What am I missing?



I would like to be able to acccess cpt['acf']['entry']['subentry']



Should I regenerate the cpt into arrays/objects in the Component state?










share|improve this question

























  • Can you update your post to include a console.log of the cpt variable after you put it in state?

    – Shawn Andrews
    Nov 27 '18 at 2:29













  • Just added the console.log() in the fetch() call and in render.

    – Mulli
    Nov 27 '18 at 4:16




















0















I have a React app that receives an object from WordPress site using fetch() over rest api (v2/posts).



The object contains an "acf" entry which holds ~30 sub entries: some arrays and some are objects. All generated with Advanced Custom Field plugin.



The application is updating this data (using this.state) and the server (fetch/post) upon user request. All is working. I am not using express, redux and the like.



My current problem is that I cannot access the internals of the "acf" entry in render() function, while I can access it within the fetch response.
I would like to be able to acccess


 cpt['acf']['entry']['subentry']

using the entry's names. But I get "cannot access property of undefined..."

Example:





// In constructor:
// this.state = {
// isLoading: false, title:"", terms:, cpt:
// }
...
fetch(url)
.then(response => {
if (response.ok)
return response.json()
throw new Error('fetchTerm: Something went wrong ...')
})
.then(cpt => {
var terms = Object.entries(cpt['acf'])
var title = Object.values(cpt['title'])

this.setState({cpt, terms, title, isLoading: false})
.then( () => {
console.log("title",this.state.cpt['title'])
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // shows ok
})

return (true) // void - no one is looking...
})
//...
render(){
if (this.state.isLoading)
return (Loading)
// occurs only after fetch resturn and this.state variables are instanciated
console.log("title", this.state.title) // shows OK
console.log("FAIL", this.state.cpt['title']) // cannot access property of NULL/Undefined...
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // same problem
}



What am I missing?



I would like to be able to acccess cpt['acf']['entry']['subentry']



Should I regenerate the cpt into arrays/objects in the Component state?










share|improve this question

























  • Can you update your post to include a console.log of the cpt variable after you put it in state?

    – Shawn Andrews
    Nov 27 '18 at 2:29













  • Just added the console.log() in the fetch() call and in render.

    – Mulli
    Nov 27 '18 at 4:16
















0












0








0








I have a React app that receives an object from WordPress site using fetch() over rest api (v2/posts).



The object contains an "acf" entry which holds ~30 sub entries: some arrays and some are objects. All generated with Advanced Custom Field plugin.



The application is updating this data (using this.state) and the server (fetch/post) upon user request. All is working. I am not using express, redux and the like.



My current problem is that I cannot access the internals of the "acf" entry in render() function, while I can access it within the fetch response.
I would like to be able to acccess


 cpt['acf']['entry']['subentry']

using the entry's names. But I get "cannot access property of undefined..."

Example:





// In constructor:
// this.state = {
// isLoading: false, title:"", terms:, cpt:
// }
...
fetch(url)
.then(response => {
if (response.ok)
return response.json()
throw new Error('fetchTerm: Something went wrong ...')
})
.then(cpt => {
var terms = Object.entries(cpt['acf'])
var title = Object.values(cpt['title'])

this.setState({cpt, terms, title, isLoading: false})
.then( () => {
console.log("title",this.state.cpt['title'])
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // shows ok
})

return (true) // void - no one is looking...
})
//...
render(){
if (this.state.isLoading)
return (Loading)
// occurs only after fetch resturn and this.state variables are instanciated
console.log("title", this.state.title) // shows OK
console.log("FAIL", this.state.cpt['title']) // cannot access property of NULL/Undefined...
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // same problem
}



What am I missing?



I would like to be able to acccess cpt['acf']['entry']['subentry']



Should I regenerate the cpt into arrays/objects in the Component state?










share|improve this question
















I have a React app that receives an object from WordPress site using fetch() over rest api (v2/posts).



The object contains an "acf" entry which holds ~30 sub entries: some arrays and some are objects. All generated with Advanced Custom Field plugin.



The application is updating this data (using this.state) and the server (fetch/post) upon user request. All is working. I am not using express, redux and the like.



My current problem is that I cannot access the internals of the "acf" entry in render() function, while I can access it within the fetch response.
I would like to be able to acccess


 cpt['acf']['entry']['subentry']

using the entry's names. But I get "cannot access property of undefined..."

Example:





// In constructor:
// this.state = {
// isLoading: false, title:"", terms:, cpt:
// }
...
fetch(url)
.then(response => {
if (response.ok)
return response.json()
throw new Error('fetchTerm: Something went wrong ...')
})
.then(cpt => {
var terms = Object.entries(cpt['acf'])
var title = Object.values(cpt['title'])

this.setState({cpt, terms, title, isLoading: false})
.then( () => {
console.log("title",this.state.cpt['title'])
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // shows ok
})

return (true) // void - no one is looking...
})
//...
render(){
if (this.state.isLoading)
return (Loading)
// occurs only after fetch resturn and this.state variables are instanciated
console.log("title", this.state.title) // shows OK
console.log("FAIL", this.state.cpt['title']) // cannot access property of NULL/Undefined...
console.log("FAMILYLOG",this.state.cpt['acf']['familylog_array']) // same problem
}



What am I missing?



I would like to be able to acccess cpt['acf']['entry']['subentry']



Should I regenerate the cpt into arrays/objects in the Component state?







reactjs rest fetch advanced-custom-fields






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 27 '18 at 3:53







Mulli

















asked Nov 27 '18 at 1:56









MulliMulli

361214




361214













  • Can you update your post to include a console.log of the cpt variable after you put it in state?

    – Shawn Andrews
    Nov 27 '18 at 2:29













  • Just added the console.log() in the fetch() call and in render.

    – Mulli
    Nov 27 '18 at 4:16





















  • Can you update your post to include a console.log of the cpt variable after you put it in state?

    – Shawn Andrews
    Nov 27 '18 at 2:29













  • Just added the console.log() in the fetch() call and in render.

    – Mulli
    Nov 27 '18 at 4:16



















Can you update your post to include a console.log of the cpt variable after you put it in state?

– Shawn Andrews
Nov 27 '18 at 2:29







Can you update your post to include a console.log of the cpt variable after you put it in state?

– Shawn Andrews
Nov 27 '18 at 2:29















Just added the console.log() in the fetch() call and in render.

– Mulli
Nov 27 '18 at 4:16







Just added the console.log() in the fetch() call and in render.

– Mulli
Nov 27 '18 at 4:16














1 Answer
1






active

oldest

votes


















0














according to your code you initialize
cpt: (which should rather be an object though) in the constructor and then you make a call to the api and only when the promise is resolved you will modify the state, the thing is it happens after the first render call is done, so you get "cannot access property of NULL/Undefined" for cpt['acf']['entry']['subentry'], though this.state.cpt['title'] will rather return undefined in the render()



Upd: To prevent this, isLoading should have been set as true in the constructor






share|improve this answer


























  • Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

    – Mulli
    Nov 27 '18 at 3:51













  • you might want to set isLoading as true when you assign it for the first time

    – Alex Tepliashin
    Nov 27 '18 at 4:10













  • You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

    – Mulli
    Nov 27 '18 at 4:22











  • Great, glad to help!

    – Alex Tepliashin
    Nov 27 '18 at 4:25












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1 Answer
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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









0














according to your code you initialize
cpt: (which should rather be an object though) in the constructor and then you make a call to the api and only when the promise is resolved you will modify the state, the thing is it happens after the first render call is done, so you get "cannot access property of NULL/Undefined" for cpt['acf']['entry']['subentry'], though this.state.cpt['title'] will rather return undefined in the render()



Upd: To prevent this, isLoading should have been set as true in the constructor






share|improve this answer


























  • Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

    – Mulli
    Nov 27 '18 at 3:51













  • you might want to set isLoading as true when you assign it for the first time

    – Alex Tepliashin
    Nov 27 '18 at 4:10













  • You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

    – Mulli
    Nov 27 '18 at 4:22











  • Great, glad to help!

    – Alex Tepliashin
    Nov 27 '18 at 4:25
















0














according to your code you initialize
cpt: (which should rather be an object though) in the constructor and then you make a call to the api and only when the promise is resolved you will modify the state, the thing is it happens after the first render call is done, so you get "cannot access property of NULL/Undefined" for cpt['acf']['entry']['subentry'], though this.state.cpt['title'] will rather return undefined in the render()



Upd: To prevent this, isLoading should have been set as true in the constructor






share|improve this answer


























  • Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

    – Mulli
    Nov 27 '18 at 3:51













  • you might want to set isLoading as true when you assign it for the first time

    – Alex Tepliashin
    Nov 27 '18 at 4:10













  • You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

    – Mulli
    Nov 27 '18 at 4:22











  • Great, glad to help!

    – Alex Tepliashin
    Nov 27 '18 at 4:25














0












0








0







according to your code you initialize
cpt: (which should rather be an object though) in the constructor and then you make a call to the api and only when the promise is resolved you will modify the state, the thing is it happens after the first render call is done, so you get "cannot access property of NULL/Undefined" for cpt['acf']['entry']['subentry'], though this.state.cpt['title'] will rather return undefined in the render()



Upd: To prevent this, isLoading should have been set as true in the constructor






share|improve this answer















according to your code you initialize
cpt: (which should rather be an object though) in the constructor and then you make a call to the api and only when the promise is resolved you will modify the state, the thing is it happens after the first render call is done, so you get "cannot access property of NULL/Undefined" for cpt['acf']['entry']['subentry'], though this.state.cpt['title'] will rather return undefined in the render()



Upd: To prevent this, isLoading should have been set as true in the constructor







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 27 '18 at 4:25

























answered Nov 27 '18 at 2:29









Alex TepliashinAlex Tepliashin

613




613













  • Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

    – Mulli
    Nov 27 '18 at 3:51













  • you might want to set isLoading as true when you assign it for the first time

    – Alex Tepliashin
    Nov 27 '18 at 4:10













  • You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

    – Mulli
    Nov 27 '18 at 4:22











  • Great, glad to help!

    – Alex Tepliashin
    Nov 27 '18 at 4:25



















  • Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

    – Mulli
    Nov 27 '18 at 3:51













  • you might want to set isLoading as true when you assign it for the first time

    – Alex Tepliashin
    Nov 27 '18 at 4:10













  • You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

    – Mulli
    Nov 27 '18 at 4:22











  • Great, glad to help!

    – Alex Tepliashin
    Nov 27 '18 at 4:25

















Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

– Mulli
Nov 27 '18 at 3:51







Please note the isLoading flag that prevents access to this.state prior to fetch() completion. As for the cpt definition. I did try to set it to an object and got same results

– Mulli
Nov 27 '18 at 3:51















you might want to set isLoading as true when you assign it for the first time

– Alex Tepliashin
Nov 27 '18 at 4:10







you might want to set isLoading as true when you assign it for the first time

– Alex Tepliashin
Nov 27 '18 at 4:10















You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

– Mulli
Nov 27 '18 at 4:22





You are right! thanks. I set it to true in componentDidMount. Just realized its better in the constructor. thanks

– Mulli
Nov 27 '18 at 4:22













Great, glad to help!

– Alex Tepliashin
Nov 27 '18 at 4:25





Great, glad to help!

– Alex Tepliashin
Nov 27 '18 at 4:25




















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