SetValidationResult helper function for updating a Knockout view model with validation errors from a simplified modelstate dictionary

gistfile1.txt

SetValidationResult: function (viewModel, modelState) {

    var trySetErrors = function (modelStateKey, modelStateErrors) {
        var keySeparator = new RegExp("[.\\[\\]]+");
        var propertyChain = modelStateKey.split(keySeparator);
        var currentObject = viewModel;
        var currentPropertyName = propertyChain.shift();
        var targetObject = null;
        while (currentObject && currentObject[currentPropertyName]) {

            if (propertyChain.length === 0) {
                targetObject = currentObject[currentPropertyName];
                break;
            }

            currentObject = ko.utils.unwrapObservable(currentObject[currentPropertyName]);
            currentPropertyName = propertyChain.shift();
        }

        // If a property that matches the key is found, update the Errors observable
        // array on that property and remove the key from the modelState object.
        if (targetObject && targetObject.Errors && ko.isObservable(targetObject.Errors)) {
            targetObject.Errors(modelStateErrors);
            return true;
        }

        return false;
    };

    // For each key in the previous modelstate that is not included in the current one, try to reset the error collection
    var lastModelState = viewModel._lastModelState;
    if (lastModelState) {
        for (var oldKey in lastModelState) {
            if (!modelState[oldKey] || modelState[oldKey].length === 0) {
                trySetErrors(oldKey, []);
            }
        }
    }

    // Save the current modelstate to be able to clear old errors on the next validation 
    viewModel._lastModelState = $.extend(true, { }, modelState); // Deep-clone with jQuery

    // Set error collection for all keys in the current modelstate
    for (var key in modelState) {
        if (trySetErrors(key, modelState[key])) {
            delete modelState[key];
        }
    }

    // All remaining current modelstate errors are "global" - add them to the ValidationSummary
    // observable array of the view model itself.
    var globalErrors = [];
    for (key in modelState) {
        globalErrors = globalErrors.concat(modelState[key]);
    }
    if (!viewModel || !viewModel.ValidationSummary || !ko.isObservable(viewModel.ValidationSummary)) {
        throw new Error("The view model does not have a 'ValidationSummary' property of type ko.observableArray, which is required to handle general validation errors.");
    }
    viewModel.ValidationSummary(globalErrors);
},