Apex: Get sObject details using ID

Id id = 'a0M7F000000qXgg';
Schema.sObjectType objType = id.getSObjectType();
Schema.DescribeSObjectResult objDescribe = objType.getDescribe();

System.debug(objDescribe.getName());

Similarly, you can get other sObject details using the methods described in the link below:
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_sobject_describe.htm

Dynamic SOQL and SOSL

To create a dynamic SOQL query at run time, use the database query method. Check the reference link for more details.

List<sObject> sobjList = Database.query(string);

To create a dynamic SOSL query at run time, use the search query method. For example:

String searchquery = 'FIND \'Edge*\' IN ALL FIELDS RETURNING Account(Id, Name), Contact, Lead';
List<List<SObject>>searchList = search.query(searchquery);

To prevent SOSL injection, use the escapeSingleQuotes method. This method adds the escape character (\) to all single quotation marks in a string that is passed in from a user. The method ensures that all single quotation marks are treated as enclosing strings, instead of database commands.

fieldList = (fieldList!=null) ? String.escapeSingleQuotes(fieldList) : fieldList;

References:
http://metillium.com/2016/03/variable-binding-in-dynamic-soql/

Salesforce Custom Settings

Custom settings are similar to custom objects and enable application developers to create custom sets of data, as well as create and associate custom data for an organization, profile, or specific user. Custom Settings data is stored in the application cache, which enables efficient access without the cost of multiple repeated queries to the database. As long as you query the Custom Settings using GET methods rather than an SOQL query you can retrieve all of the values with literally zero impact on the governor’s count of the number of queries performed or rows retrieved.

List Custom Settings

It provides a reusable set of static data that can be accessed across your organization. Data in list settings does not vary with profile or user, but is available organization-wide.

The following are instance methods for list custom settings.

• getAll(): Returns a map of the data sets defined for the custom setting.
• getInstance(dataSetName) / getValues(dataSetName): Returns the custom setting data set record for the specified data set name.

Hierarchy Custom Settings

It uses a built-in hierarchical logic that lets you "personalize" settings for specific profiles or users. The hierarchy logic checks the organization, profile, and user settings for the current user and returns the most specific value. In the hierarchy, settings for an organization are overridden by profile settings, which, in turn, are overridden by user settings.

References:
http://www.brcline.com/blog/salesforce-custom-settings
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_custom_settings.htm

Lightning Component for attaching files using input file component

A rough markup of this component using input type file component. Please refer the previous article to get an idea of how the helper JS and the apex class is formed.

<div class="slds-form-element">
    <span class="slds-form-element__label" id="file-selector-id">Attachment</span>
    <div class="slds-form-element__control">
        <div class="slds-file-selector slds-file-selector_files">
            <div class="slds-file-selector__dropzone">
                <input type="file" class="slds-file-selector__input slds-assistive-text" accept="image/png" id="file-upload-input-01" aria-describedby="file-selector-id" aura:id="file" onchange="{!c.showfile}"/>
                <label class="slds-file-selector__body" for="file-upload-input-01">
                    <span class="slds-file-selector__button slds-button slds-button_neutral">
                        <c:svgIcon class="slds-button__icon slds-button__icon_left" xlinkHref="/resource/slds232/assets/icons/utility-sprite/svg/symbols.svg#upload" />
                        Upload Files
                    </span>
                    <span class="slds-file-selector__text slds-medium-show">or Drop Files</span>
                </label>
            </div>
        </div>
    </div>
</div>

showfile:function(component,event,helper){
    helper.show(component,event);
    
    var f = event.target.files[0]; 
    var fileInput = component.find("file").getElement();
    var file = fileInput.files[0];
    
    var reader = new FileReader();
    reader.onloadend = function(e) {
        var contents = e.target.result;
        var base64Mark = 'base64,';
        var dataStart = contents.indexOf(base64Mark) + base64Mark.length;
        var fileContents = contents.substring(dataStart);
        
        helper.upload(component, file, encodeURIComponent(fileContents), function(answer) {
            if (answer) {
                helper.hide(component,event);
            }
            else{
            }
        });
    }
    reader.readAsDataURL(file);
}

Lightning Component for attaching files using lightning:input

<aura:component description="FileUploader" controller="FileUploadController">
    <aura:attribute name="fileToBeUploaded" type="Object[]"/>
    <lightning:spinner aura:id="mySpinner" class="slds-hide"/>
    
    <div class=" slds-box">
        <div class="slds-grid slds-wrap">
            <lightning:input aura:id="file-input" type="file"
                             files="{!v.fileToBeUploaded}"
                             onchange="{!c.onFileUploaded}"
                             accept="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                             label="Attachment"
                             name="file" multiple="true"/>
        </div>
    </div>
</aura:component>

({
    onFileUploaded:function(component,event,helper){
        helper.show(component,event);
        var files = component.get("v.fileToBeUploaded");
        if (files && files.length > 0) {
            var file = files[0][0];
            var reader = new FileReader();
            reader.onloadend = function() {
                var dataURL = reader.result;
                var content = dataURL.match(/,(.*)$/)[1];
                helper.upload(component, file, content, function(answer) {
                    if (answer) {
                        helper.hide(component,event);
                        // Success
                    }
                    else{
                        // Failure
                    }
                });
            }
            reader.readAsDataURL(file);
        }
        else{
            helper.hide(component,event);
        }
    }
})

({
    upload: function(component, file, base64Data, callback) {
        var action = component.get("c.uploadFile");
        console.log('type: ' + file.type);
        action.setParams({
            fileName: file.name,
            base64Data: base64Data,
            contentType: file.type
        });
        action.setCallback(this, function(a) {
            var state = a.getState();
            if (state === "SUCCESS") {
                callback(a.getReturnValue());
            }
        });
        $A.enqueueAction(action);
    },
    show: function (cmp, event) {
        var spinner = cmp.find("mySpinner");
        $A.util.removeClass(spinner, "slds-hide");
        $A.util.addClass(spinner, "slds-show");
    },
    hide:function (cmp, event) {
        var spinner = cmp.find("mySpinner");
        $A.util.removeClass(spinner, "slds-show");
        $A.util.addClass(spinner, "slds-hide");
    }
})

public class FileUploadController {
    @AuraEnabled
    public static Id uploadFile(String fileName, String base64Data, String contentType) { 
        base64Data = EncodingUtil.urlDecode(base64Data, 'UTF-8');
        Attachment a = new Attachment();
        a.parentId = '0017F000007xoiVQAQ';
        a.Body = EncodingUtil.base64Decode(base64Data);
        a.Name = fileName;
        a.ContentType = contentType; 
        insert a;
        System.debug(a.Id);
        return a.Id;
    }
}

NOTE: For demo purpose, I have hardcoded the value of an account '0017F000007xoiVQAQ' in the apex class. In actual scenario, you should get this ID from the component.