Blob Functions

Convert base64 encoded string to blob

persistent object CropQualityPicture {
	blob image;
	string imageStr;
}

// Convert base64 string to blob
cropQualityPicture.image = Blob:fromString(cropQualityPicture.imageStr);

Convert blob to base64 encoded string

Similarly to the above, blobs can also be converted to base64 encoded strings:

// Convert blob to base64 string
cropQualityPicture.imageStr = Blob:toString(cropQualityPicture.image);

Convert base64 encoded string to a wrapped blob

Since blob fields on objects are automatically accompanied by meta attributes that describe the mime type, file size and file name, an additional conversion is available where a base64 encoded string can be converted to a built-in object that wraps the blob and includes the above mentioned meta fields automatically:

MezBlobResult blobWrapper = Blob:wrapFromString(cropQualityPicture.imageStr, "image/jpeg", "file_name_str");

// This assignment will assign the blob field and also copy the meta fields
cropQualityPicture.image = blobWrapper.blobData;

// Built-in wrapper object
object MezBlobResult {
	blob blobData;

	// blobData_mtype__, blobData_fname__, blobData_size__, are included by default
}

Download a file for a blob

Blobs can also be downloaded as files on the frontend. One method is to use the file browser widget.

Another, more flexible, method is with the Mez:downloadFile built-in function.

By calling the built-in function and providing an object that contains the blob attribute, a file download will trigger when navigating or when reloading the current view.

As an example, see the following action triggered from a frontend submit button:

</submit>
	<submit label="submit.download_selected" action="downloadSelectedCropQualityPicture">
</submit>

DSL_VIEWS downloadSelectedCropQualityPicture() {
	if(selectedCropQualityPicture == null) {
		Mez:alertWarn("alert_warn.no_images_selected");
		return null;
	}

	// Last parameter representing file name is optional 
	// If not specified _fname__ field will be used as the file name
	Mez:downloadFile(selectedCropQualityPicture, "image", getFileName());

	// Any navigation even to the same view will trigger the file download
	return null;
}

Generate a CSV blob from a collection

To programatically generate a CSV blob from a collection the Mez:collectionCsv built-in function can be used. The file name (file extension excluded) and collection are required as arguments.

Additionally, a comma separated list of fields names can be specified if not all fields are to be included in the file. Field names will be used a column headings.

The resulting blob will be wrapped in the built-in MezBlobResult object. 

// Generate a CSV for only description and mobilenumber fields
MezBlobResult result = Mez:collectionCsv("shops_slim", shops, "description,mobilenumber");

// Generate a CSV for all fields
MezBlobResult result = Mez:collectionCsv("shops_fat", shops);

MyCsvBlob myBlob = CsvBlob:new();
myBlob.data = result.blobData;
myBlob.save();