How to use RCTConvert in react

Question

I am new to react and working on react bridging modules. I just want to know that how the RCTConvert is useful and how can use that. I am following this site link

Please, anyone helps me to know about this stuff.

It looks like that class is to help pass various data types from the native side of the code into a JSON data type that can be handle by the javascript on the react-native side. Do you have a specific question about it? — Jason Gaare, Sep 15 '16 at 14:30
I just want to know the difference between NSString *location = details[@"location"]; NSLog(@"location ==========>>%@",location); NSString *location1 = [RCTConvert NSString:details[@"location"]]; NSLog(@"location1 is ==========>>%@",location1); In both cases I'm getting the same output. — Ramakrishna, Sep 16 '16 at 04:43
Sorrry I don't know much about the difference. If you're getting the same output does that affect you? — Jason Gaare, Sep 16 '16 at 14:13
After searching google, I found that it is used to convert JSON Objects into native types. Here the link http://cocoadocs.org/docsets/React/0.2.0/Classes/RCTConvert.html — Ramakrishna, Sep 19 '16 at 04:52

score 4 · Answer 1 · answered Jun 10 '21 at 11:07

The RCTConvert helper functions all accept a JSON value as input and map it to a native Objective-C type or class. It's useful to convert basic supported input parameter types such as NSString, NSNumber, NSArray, NSDictionary to other ones: NSURL, UIColor, CGRect etc. which are not supported by the React bridge. For instance:

Java Script:

Module.setPosition({x : 10, y: 20});

ObjC:

RCT_EXPORT_METHOD(setPosition:(id)position) {
    CGPoint point = [RCTConvert CGPoint:position];
    NSLog(@"x: %f, y: %f", point.x, point.y);
}

// Prints: x: 10.000000, y: 20.000000

Also it's possible to extend RCTConvert with RCT_CUSTOM_CONVERTER macro for your custom types:

Java Script:

Module.addUser({name : 'John', email: 'joghn@domain.com'});

ObjC:

typedef struct {
    NSString* name;
    NSString* email;
} User;

User createUser(NSString* name, NSString* email) {
    User user;
    user.name = name;
    user.email = email;
    return user;
};

@implementation RCTConvert (User)

RCT_CUSTOM_CONVERTER(User, User, createUser(json[@"name"], json[@"email"]) )

@end

...

RCT_EXPORT_METHOD(addUser:(id)user) {
    User new_user = [RCTConvert User:user];
    NSLog(@"name: %@, email: %@", new_user.name, new_user.email);
}

// Prints: name: John, email: joghn@domain.com

For simple types such as NSString it does type checking and rices the conversion error if you try to cast to the other type so that is very important in debugging. This is code for that from the sources:

RCTConvert.h

+ (NSString *)NSString:(id)json;

RCTConvert.m

/**
 * This macro is used for creating converter functions for directly
 * representable json values that require no conversion.
 */
#if RCT_DEBUG
#define RCT_JSON_CONVERTER(type)             \
  +(type *)type : (id)json                   \
  {                                          \
    if ([json isKindOfClass:[type class]]) { \
      return json;                           \
    } else if (json) {                       \
      RCTLogConvertError(json, @ #type);     \
    }                                        \
    return nil;                              \
  }
#else
#define RCT_JSON_CONVERTER(type) \
  +(type *)type : (id)json       \
  {                              \
    return json;                 \
  }
#endif

RCT_JSON_CONVERTER(NSArray)
RCT_JSON_CONVERTER(NSDictionary)
RCT_JSON_CONVERTER(NSString)
RCT_JSON_CONVERTER(NSNumber)

For more samples how to use RCTConvert you can look at the sources: https://github.com/facebook/react-native/blob/master/React/Base/RCTConvert.m

How to use RCTConvert in react

1 Answers1