CODEWITHSUNDEEP
typescriptthis
BENBUN Coder
BENBUN Coder

Reputation: 4881

Cannot read property of undefined - method call within a class

I have a typescript class that contains the following 

getOrgList(oo: fhir.Organization) {
    var olist: orgRoles[] = [];
    var filtered = oo.extension.filter(this.getRoleExt);

    filtered.forEach(function (value) {
        var org = new orgRoles();
        value.extension.forEach(function (innerValue) {
            switch (innerValue.url) {
                case 'role':
                    org.roleName = innerValue.valueCoding.display;
                    break;
                case 'primaryRole':
                    org.primaryRole = innerValue.valueBoolean;
                    break;
                case 'activePeriod':
                    var periodType = innerValue.valuePeriod.extension[0].valueString;
                    var periodExt = innerValue.valuePeriod;
                    var periodDisplay= this.getPeriodDisplay(periodExt);
                    break;
                case 'status':
                    org.activeStatus = innerValue.valueString;
                    break;
            }
        });

        olist.push(org);
    });

    return olist;
}

This is currently failing on the line

var periodDisplay= this.getPeriodDisplay(periodExt);

With an error 

 ERROR TypeError: Cannot read property 'getPeriodDisplay' of undefined

However, getPeriodDisplay is defined as the next method in the same class.

getPeriodDisplay(pp) {
    return "++++";
}

I have other code that calls getPeriodDisplay() from outside the class, but calling it from a different method within the class seems to cause the problem

Any ideas on how I should address this?

Upvotes: 0

Views: 1597

Answers (1)

Dmitriy
Dmitriy

Reputation: 2822

You need to switch regular functions for arrow functions to have access to correct this (class instance):

getOrgList(oo: fhir.Organization) {
    var olist: orgRoles[] = [];
    var filtered = oo.extension.filter(this.getRoleExt);

    filtered.forEach((value) => {
        var org = new orgRoles();
        value.extension.forEach((innerValue) => {
            switch (innerValue.url) {
                case 'role':
                    org.roleName = innerValue.valueCoding.display;
                    break;
                case 'primaryRole':
                    org.primaryRole = innerValue.valueBoolean;
                    break;
                case 'activePeriod':
                    var periodType = innerValue.valuePeriod.extension[0].valueString;
                    var periodExt = innerValue.valuePeriod;
                    var periodDisplay= this.getPeriodDisplay(periodExt);
                    break;
                case 'status':
                    org.activeStatus = innerValue.valueString;
                    break;
            }
        });

        olist.push(org);
    });

    return olist;
}

Upvotes: 1

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