Allow setting custom Content-Type within multi-part forms

[smartt]

I had a case when working with an API where I needed to specifically set the Content-Type (from "application/octet-stream" to "image/jpeg". As a quick hack, I implemented it this way [on the feat_45 branch]:

diff --git a/src/ios/RNFetchBlobReqBuilder.m b/src/ios/RNFetchBlobReqBuilder.m
index df4c3d1..6b44b74 100644
--- a/src/ios/RNFetchBlobReqBuilder.m
+++ b/src/ios/RNFetchBlobReqBuilder.m
@@ -134,6 +134,7 @@
         {
             NSString * name = [field valueForKey:@"name"];
             NSString * content = [field valueForKey:@"data"];
+            NSString * contentType = [field valueForKey:@"type"];
             // field is a text field
             if([field valueForKey:@"filename"] == nil || content == [NSNull null]) {
                 [formData appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
@@ -155,7 +156,7 @@
                             NSString * filename = [field valueForKey:@"filename"];
                             [formData appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
                             [formData appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"%@\"\r\n", name, filename] dataUsingEncoding:NSUTF8StringEncoding]];
-                            [formData appendData:[[NSString stringWithFormat:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
+                            [formData appendData:[[NSString stringWithFormat:@"Content-Type: %@\r\n\r\n", contentType] dataUsingEncoding:NSUTF8StringEncoding]];
                             [formData appendData:content];
                             [formData appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
                             i++;
@@ -174,7 +175,7 @@
                 NSString * filename = [field valueForKey:@"filename"];
                 [formData appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
                 [formData appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"%@\"\r\n", name, filename] dataUsingEncoding:NSUTF8StringEncoding]];
-                [formData appendData:[[NSString stringWithFormat:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
+                [formData appendData:[[NSString stringWithFormat:@"Content-Type: %@\r\n\r\n", contentType] dataUsingEncoding:NSUTF8StringEncoding]];
                 [formData appendData:blobData];
                 [formData appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
             }

..and used it like this:

            RNFetchBlob.fetch('POST', url, {
                Authorization: `Bearer ${token}`,
                Accept: "application/json",
                "Content-Type": "multipart/form-data",
            }, [
                {
                    name: 'image',
                    filename: filename,
                    data: RNFetchBlob.wrap(asset.uri),
                    "type": 'image/jpeg',
                },
                {
                    name: "someOtherField",
                    data: JSON.stringify({foo: 1, bar: 2}),
                    "type": "application/json",
                },

I figured you might want to implement it different so that it's optional, and works on Android, so no PR currently :-)

[wkh237]

Hi @smartt , great thank you for your help, I think this is great, I'll add this to feat_45 branch 😄

[wkh237]

@smartt this change has been merged into feat_45. Please see 2e35075.

[wkh237]

Hi @smartt , I've released 0.6.2 which implemented this feature, please check if it work as expected, thank you 😏

[smartt]

Working for me in the emulator! Thank you--this is fantastically helpful!

[wkh237]

Great ! I'm glad I could help 😄