The function is attempting to access the 'lockDatabase' property of an undefined object, resulting in an error

I'm encountering an error due to the scope issue with 'this', and I'm struggling to find a solution. I attempted using the fat arrow, which solved the scope problem but created another issue where I lack a callback value that needs to be utilized. Below is the snippet of my code:

this.checkIfDatabaseIsLocked(function(res) {
          //If true database is locked
          console.log("result checkIfDatabaseIsLocked: " + res);
          if (res) {
            return;
          }
          //LockDatabase
          this.lockDatabase().then(
            result => {

Any suggestions on how to overcome this challenge? Thank you in advance!!!

javascriptangulartypescript

Answer №1

Implementing an arrow function in this scenario is crucial to maintain the expected value of this:

this.verifyIfDatabaseIsBlocked(responseHandler => {
      // If the database is blocked
      console.log("Result from verifying if Database Is Blocked: " + responseHandler);
      if (responseHandler) {
        return;
      }
      // Proceed with blocking the database
      this.blockDatabase().then(
        outcome => {
... and so forth

Answer №2

To ensure the correct this context inside your function, you can utilize arrow functions or bind your function accordingly:

this.checkIfDatabaseIsLocked((res) => {
    // The context of `this` will be properly bound here
})

Another option is to use Function.bind:

this.checkIfDatabaseIsLocked((function (res) {
    // The context of `this` will be correctly bound here
}).bind(this))

Avoid using Function.bind in TypeScript as it may lead to a loss of type checking. For more information, refer to https://github.com/Microsoft/TypeScript/issues/212

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