Objective-C

Call a JavaScript Function Returning a String

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Demonstrates how to call a JavaScript function that returns a string. Objective-C

#import <CkoStringBuilder.h>
#import <CkoJs.h>
#import <CkoJsonObject.h>
#import <NSString.h>

BOOL success = NO;

// This is the JavaScript function we'll call:

// function greet(name) {
//     return "Hello, " + name + "!";
// }

CkoStringBuilder *sbScript = [[CkoStringBuilder alloc] init];
[sbScript Append: @"function greet(name) { return \"Hello, \" + name + \"!\"; }"];

CkoJs *js = [[CkoJs alloc] init];

CkoJsonObject *result = [[CkoJsonObject alloc] init];
result.EmitCompact = NO;

// Call Eval to add the function to the context's global object
success = [js Eval: sbScript result: result];
if (success == NO) {
    // Examine the result for an exception.
    NSLog(@"%@",[result Emit]);

    // Also examine the LastErrorText.
    NSLog(@"%@",js.LastErrorText);
    return;
}

// ------------------------------------------------------------------------------
// Call the function greet("Michael")

CkoJsonObject *funcCall = [[CkoJsonObject alloc] init];

// Create JSON specifying the function name and arguments

// {
//   "name": "greet",
//   "args": [ "Michael" ]
// }

[funcCall UpdateString: @"name" value: @"greet"];
[funcCall UpdateString: @"args[0]" value: @"Michael"];

success = [js CallFunction: funcCall result: result];
if (success == NO) {
    // Examine the result for an exception.
    NSLog(@"%@",[result Emit]);

    // Also examine the LastErrorText.
    NSLog(@"%@",js.LastErrorText);
    return;
}

NSLog(@"%@",[result Emit]);

// Output:
// {
//   "type": "string",
//   "value": "Hello, Michael!"
// }

NSString *retval = [result StringOf: @"value"];
NSLog(@"%@",retval);

// Output:
// Hello, Michael!