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Compiler complains object is possibly undefined after assigning a value #31060
Description
Activity
Our flow control analysis isn't built to detect this kind of complementarity.
The equivalent form
if (someParam === undefined) { if (someOtherParam === undefined) throw new Error("One of the params must be provided."); someParam = someOtherParam.prop; }
doesn't produce an error.
In fact, below snippet won't produce an error too:
interface SomeObject { prop: string } interface SomeComplexObject { prop: SomeObject } export class SomeClass { private prop: String; public constructor(someParam?: SomeObject, someOtherParam?: SomeComplexObject) { if (someParam !== undefined) { // <1> // No op } else if (someOtherParam !== undefined) { // <2> someParam = someOtherParam.prop; } else { throw new Error("One of the params must be provided."); } // If someParam === undefined, someOtherParam === undefined, it should goes to <1> and throw; // If someParam === undefined, it should goes to <2>, then someParam will be assigned with a non-undefined value, then goes to <3>; // If someParam !== undefined, it should goes to <3> directly and should not generate any error. // <3> this.prop = someParam.prop; // More statements using someParam... } }
Since I have ~5-6 statements using
someParamand I prefer not to put them in an if-else block, I will use this one to workaround.
why does the above check not prevent this error?
ah workaround
tx.btc_volume!why does the above check not prevent this error?
ah workaround
tx.btc_volume!Guess the compiler is complaining about
tx.btc_volumemight be undefined, nottx.Yiwen Wang (@yhvicey) yes you were right. If i put the bang in the right place it shuts up
tx.btc_volume!I guess this will be a TS difference from the new JS feature with
tx?.btc_volume?to fail out and not have to keep checking nulls. like coffeescript had many years ago...In your tsconfig.js
"strictNullChecks": false,
"strict": false,Reacted by Stan Konnov, Washington Soares, Alex Vishnevsky and Nikolay RomashkoReacted by Washington Soares, Reid Kersey and Evgeny TimoshenkoReacted by Eugene Povetkinlook i have an angular code like this
this.titleService.setTitle(this.SinglePost[0]['title']['rendered']);and its sowing me an error like
ERROR in src/app/blog/blog.component.ts(93,40): error TS2532: Object is possibly 'undefined'.
src/app/blog/blog.component.ts(93,56): error TS2339: Property '0' does not exist on type '[]'.
so i got a solution of it
var index =0; this.titleService.setTitle(this.SinglePost[index]['title']['rendered']);and now its working fine
I get an error saying: src/main/webapp/app/entities/local/newmenu-update.component.html(1,18137): Object is possibly 'null'. (when I deploy to heroku)
But there is no line number 18137 in newmenu-update.component.html, so the question is: How can I find out where the problem is? I get like a 50+ of this errors in the same page.
Also the issue exists when we have the following code:
function someChecking(value?: {}) { const rules = { key1: "v1", key2: "v2"} if (!value) { return false; } // allright this is nested function function isRuleFailed(ruleKey: string): any { // I get 'possible undefined' here - but it's wrong because function fired after checking value return value[ruleKey]; } return isRuleFailed('required') || Object.keys(value).find(isRuleFailed) }
Reacted by Suhaib MujahidI have the same issue as Yegor (@Yegorich555).
if (progress === undefined) return null; // Object is possibly 'undefined'. TS2532 if (progress.total === 0) return something;
This is not the thread to post every "I got an 'object is possibly undefined' error".
Note that narrowing doesn't occur in unreachable code; if your code cannot be reached by any execution path, then you may see errors as a result.
Please post self-contained bugs if you feel you've encountered an error you shouldn't have, or use Stack Overflow to help understand why you're seeing a particular error. Thanks!
- locked as off topic and limited conversation to collaborators
on Mar 10, 2020
TypeScript Version: 3.5.0-dev.20190420
Search Terms:
Object is possibly 'undefined'Code
Expected behavior:
someParamwon't beundefinedand its props can be accessedActual behavior:
Compiler complains
Object is possibly 'undefined'Playground Link: Playground (Need to check strictNullCheck)
Related Issues: Not yet