My goal in Smalltalk: Creating a Scheme Handler for a Method Browser

A programming language reaches a “tipping point” when a developer strongly prefers it to their previous language, often the implementation language. This point is characterized by a desire to use the new language exclusively for new development, even if it still has limitations.

The author describes reaching this tipping point with Objective-Smalltalk while working on a Smalltalk-inspired method browser for live coding environments (AppLive and SiteBuilder).

The current implementation of the method browser is tightly coupled and requires an overhaul.

The author is exploring leveraging scheme handlers to enable external editing of classes and methods.

The following Objective-Smalltalk code demonstrates the desired functionality:

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#!/usr/local/bin/stsh
#-methodbrowser:classdef


scheme ClassBrowser  {
  var dictionary.
  -initWithDictionary:aDict {
     self setDictionary:aDict.
     self.
  }
  -classDefs {
     self dictionary at:'methodDict'.
  }
  /. { 
     |= {
       self classDefs allKeys.
     }
  }

  /:className/:which/:methodName  { 
     |= {
       self classDefs at:className | at:which | at:methodName.
     }
     =| {
       self classDefs at:className | at:which | at:methodName put:newValue.
     }
  }

  /:className/:which { 
     |= {
       self classDefs at:className | at:which | allKeys.
     }
  }

}

scheme:browser := ClassBrowser alloc initWithDictionary: classdef value propertyList.
stdout do println: browser:. each. 
shell runInteractiveLoop. 

Although the Objective-Smalltalk code needs further refinement, the author considers it more expressive and concise than the equivalent Objective-C implementation.

The author expresses a strong aversion to rewriting the code in Objective-C, even though AppLive and SiteBuilder are Objective-C projects. This reluctance highlights the significant advantage of using Objective-Smalltalk for this task.

For comparison, the original Objective-C code is provided below:

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//
//  MethodDict.h
//  MPWTalk
//
//  Created by Marcel Weiher on 10/16/11.
//  Copyright (c) 2012 Marcel Weiher. All rights reserved.
//

#import @protocol MethodDict -(NSArray*)instanceMethodsForClass:(NSString*)className;
-(NSArray*)classMethodsForClass:(NSString*)className;

-(NSString*)fullNameForMethodName:(NSString*)shortName ofClass:(NSString*)className;
-(NSString*)methodForClass:(NSString*)className methodName:(NSString*)methodName;
-(void)setClassMethod:(NSString*)methodBody name:(NSString*)methodName  forClass:(NSString*)className;
-(void)setInstanceMethod:(NSString*)methodBody name:(NSString*)methodName  forClass:(NSString*)className;

-(void)deleteInstanceMethodName:(NSString*)methodName forClass:(NSString*)className;
-(void)deleteClassMethodName:(NSString*)methodName forClass:(NSString*)className;

-(NSMutableDictionary*)addClassWithName:(NSString*)newClassName;
-(void)deleteClass:(NSString*)className;

-(NSString*)instanceMethodForClass:(NSString*)className methodName:(NSString*)methodName;
-(NSString*)classMethodForClass:(NSString*)className methodName:(NSString*)methodName;

@end



@interface MethodDict : NSObject {
    NSMutableDictionary *dict;
}


- (NSDictionary *)dict;
-initWithDict:(NSDictionary*)newDict;


-(NSArray*)classes;


@end



//
//  MethodDict.m
//  MPWTalk
//
//  Created by Marcel Weiher on 10/16/11.
//  Copyright (c) 2012 Marcel Weiher. All rights reserved.
//

#import "MethodDict.h"
#import #import @implementation NSString(methodName)

-methodName
{
    MPWMethodHeader *header=[MPWMethodHeader methodHeaderWithString:self];
    return [header methodName];
}

@end

@implementation MethodDict

objectAccessor(NSMutableDictionary, dict, setDict)


-initWithDict:(NSDictionary*)newDict
{
    self = [super init];
    [self setDict:[[newDict mutableCopy] autorelease]];
    return self;
}

-(NSData*)asXml
{
    NSData *data=[NSPropertyListSerialization dataFromPropertyList:[self dict] format:NSPropertyListXMLFormat_v1_0 errorDescription:nil];
    return data;
}

-(NSArray*)classes
{
    return [[[self dict] allKeys] sortedArrayUsingSelector:@selector(compare:)];
}

-(NSMutableDictionary*)classDictForName:(NSString*)className
{
    return [[self dict] objectForKey:className];
}

-(void)deleteClass:(NSString*)className
{
    return [[self dict] removeObjectForKey:className];
}

-(NSMutableDictionary*)methodDictForClass:(NSString*)className classMethods:(BOOL)isClassMethod
{
    NSString *key=isClassMethod ? @"classMethods" : @"instanceMethods";
    
    return [[[self dict] objectForKey:className] objectForKey:key];
}



-(NSArray*)methdodsForClass:(NSString*)className getClassMethods:(BOOL)classMethods
{
    NSDictionary *methodDict=[self methodDictForClass:className classMethods:classMethods];
    NSArray* methodKeys = [methodDict allKeys];
    if ( [methodKeys count]) {
        return [(NSArray*)[[methodKeys collect] methodName] sortedArrayUsingSelector:@selector(compare:)];
    }
    return [NSArray array];
}

-(NSArray*)instanceMethodsForClass:(NSString*)className
{
    return  [self methdodsForClass:className getClassMethods:NO];
}

-(NSArray*)classMethodsForClass:(NSString*)className
{
    return  [self methdodsForClass:className getClassMethods:YES];
}


-(NSString*)fullNameForMethodName:(NSString*)shortName ofClass:(NSString*)className
{
    NSArray *fullNames = [[self methodDictForClass:className classMethods:NO] allKeys];
    fullNames=[fullNames arrayByAddingObjectsFromArray:[[self methodDictForClass:className classMethods:YES] allKeys]];
    for ( NSString *fullName in fullNames ) {
        if ( [[fullName methodName] isEqual:shortName] ) {
            return fullName;
        }
    }
    return nil;
}

-(NSString*)instanceMethodForClass:(NSString*)className methodName:(NSString*)methodName
{
    
    return [[self methodDictForClass:className classMethods:NO] objectForKey:[self fullNameForMethodName:methodName ofClass:className]];
}

-(NSString*)classMethodForClass:(NSString*)className methodName:(NSString*)methodName
{
    
    return [[self methodDictForClass:className classMethods:YES] objectForKey:[self fullNameForMethodName:methodName ofClass:className]];
}

-(NSString*)methodForClass:(NSString*)className methodName:(NSString*)methodName
{
    
    return [self instanceMethodForClass:className methodName:methodName];
}


-(void)setMethod:(NSString*)methodBody name:(NSString*)methodName  forClass:(NSString*)className isClassMethod:(BOOL)isClassMethod
{
    NSMutableDictionary *methodDict = [self methodDictForClass:className classMethods:isClassMethod];
    if ( !methodDict ) {
        [self addClassWithName:className];
        methodDict = [self methodDictForClass:className classMethods:isClassMethod];
    }
    [methodDict setObject:methodBody forKey:methodName];
}

-(void)setClassMethod:(NSString*)methodBody name:(NSString*)methodName  forClass:(NSString*)className
{
    [self setMethod:methodBody name:methodName forClass:className isClassMethod:YES];
}

-(void)setInstanceMethod:(NSString*)methodBody name:(NSString*)methodName  forClass:(NSString*)className
{
    [self setMethod:methodBody name:methodName forClass:className isClassMethod:NO];
}

-(NSMutableDictionary*)addClassWithName:(NSString*)newClassName
{
    NSMutableDictionary *classDict=[self classDictForName:newClassName];
    if ( !classDict) {
        classDict=[NSMutableDictionary dictionary];
        classDict[@"instanceMethods"]=[NSMutableDictionary dictionary];
        classDict[@"classMethods"]=[NSMutableDictionary dictionary];
        dict[newClassName]=classDict;
    }
    return classDict;
}


-(void)deleteMethodName:(NSString*)methodName forClass:(NSString*)className isClassMethod:(BOOL)isClassMethod
{
    NSMutableDictionary *methodDict = [self methodDictForClass:className classMethods:isClassMethod];

    [methodDict removeObjectForKey:[self fullNameForMethodName:methodName ofClass:className]];
}

-(void)deleteInstanceMethodName:(NSString*)methodName forClass:(NSString*)className
{
    [[self methodDictForClass:className classMethods:NO] removeObjectForKey:[self fullNameForMethodName:methodName ofClass:className]];
}

-(void)deleteClassMethodName:(NSString*)methodName forClass:(NSString*)className
{
    [[self methodDictForClass:className classMethods:YES] removeObjectForKey:[self fullNameForMethodName:methodName ofClass:className]];
}

-(NSString*)description
{
    return [NSString stringWithFormat:@"<%@:%p: %@>",[self class],self,dict];
}

@end 

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